INTERNATIONAL  MEDICAL  MONOGRAPHS 

rDR.  LEONARD  HILL,  F.R.S. 
General  Editors  |DR    WlLUAM  BULLOCH 


THE 

MECHANICAL  FACTORS 
OF  DIGESTION 


BY 

WALTER  B.  CANNON,  A.M.,  M.D. 

GEORGE   HIGGINSON    PROFESSOR   OF    PHYSIOLOGY 
HARVARD   UNIVERSITY 


ILLUSTRATED 


LONDON 

EDWARD    ARNOLD 

NEW  YORK  :  LONGMANS,  GREEN  &  CO. 

1911 

(A  II  rights  res  erred 


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TO    THE    MEMORY    OF 

PROFESSOR  HENRY  PICKERING  BOWDITCH 

IS    GRATEFULLY   DEDICATED 

THIS    ACCOUNT    OF    RESEARCHES   BEGUN 

UNDER  HIS  INSPIRATION 


V 


GENERAL   EDITORS'    PREFACE 

THE  Editors  hope  to  issue  in  this  series  of  International  Medical 
Monographs  contributions  to  the  domain  of  the  Medical  Sciences 
on  subjects  of  immediate  interest,  made  by  first-hand  authorities 
who  have  been  engaged  in  extending  the  confines  of  knowledge. 
Readers  who  seek  to  follow  the  rapid  progress  made  in  some 
new  phase  of  investigation  will  find  herein  accurate  information 
acquired  from  the  consultation  of  the  leading  authorities  of 
Europe  and  America,  and  illuminated  by  the  researches  and 
considered  opinions  of  the  authors. 

Amidst  the  press  and  rush  of  modern  research,  and  the  multi- 
tude of  papers  published  in  many  tongues,  it  is  necessary  to  find 
men  of  proved  merit  and  ripe  experience  who  will  winnow  the 
wheat  from  the  chaff,  and  give  us  the  present  knowledge  of  their 
own  subjects  in  a  duly  balanced,  concise,  and  accurate  form. 
In  this  the  first  volume  of  the  series  Professor  Cannon  deals  with 
the  Mechanical  Factors  of  Digestion.  Professor  Cannon  initiated 
the  method  of  studying  the  movements  of  the  bowels  by  means 
of  the  Rontgen  rays,  and  all  subsequent  researches  have  been 
based  on  his  discoveries.  We  confidently  expect  that  this  valu- 
able monograph,  containing  the  fruit  of  many  years'  work,  will 
prove  of  the  greatest  interest  and  help  to  those  seeking  to  under- 
stand a  subject  which  is  of  the  first  importance  in  Practical 

Medicine. 

LEONARD  HILL, 
WILLIAM  BULLOCH. 

October,  1911. 


PREFACE 

RESEARCHES  conducted  by  the  writer  and  his  collaborators  in 
the  Physiological  Laboratory  of  Harvard  University  during  the 
past  ten  years  form  the  basis  of  this  book.  In  describing  these 
researches,  the  related  work  of  other  investigators  has  also  been 
incorporated,  and  although  the  exposition  of  the  subject  is  not 
intended  to  be  encyclopedic,  the  whole  presents  an  account  of 
the  mechanical  activities  of  the  alimentary  canal  as  they  are 
now  known  and  understood.  The  plan  here  followed  runs  the  risk 
of  emphasizing  unduly  a  single  series  of  investigations  ;  but,  on 
the  other  hand,  it  has  the  advantage  of  offering  mainly  direct 
testimony  rather  than  secondary  interpretation. 

Most  of  the  original  accounts  of  the  experiments  in  the  Harvard 
Physiological  Laboratory  have  appeared  in  American  journals 
devoted  to  the  medical  sciences.  Much  of  the  material  which 
now  appears  in  Chapters  XIV.  and  XV.  has  not  previously  been 
published,  except  in  brief  notes  in  the  Proceedings  of  the  American 
Physiological  Society. 

The  hope  of  everyone  who  has  tried  to  extend  the  boundaries 
of  knowledge  is  that  others  will  soon  take  up  the  work  where  he 
has  dropped  it ;  and  if  this  book  should  by  chance  stimulate 
further  investigation,  its  most  cherished  object  will  have  been 

attained. 

WALTER  B.  CANNON. 

BOSTON,  MASSACHUSETTS, 
July,  1911. 


CONTENTS 


CHAPTER  I 

GENERAL  FEATURES  OF  THE  MOVEMENTS  OF  THE  ALIMENTARY 
CANAL,  AND  METHODS  OF  INVESTIGATION 

PAGES 

Functions  of  the  gastro-intestinal  movements— -Propelling  food,  mixing 
food  and  secretions,  exposing  digested  food  for  absorption — Uni- 
formity of  structure  of  canal — Uniformity  of  action — Peristalsis — 
Extrinsic  control — Methods  of  studying  the  movements  ;  fistulae, 
exposure  under  warm  salt  solution,  X  rays — Details  of  X-ray 
procedure  -  -  -  ...  .  1 — 7 


CHAPTER  II 
THE  MOVEMENTS  OF  MASTICATION  AND  DEGLUTITION 

Movements  of  mastication  :  Duration — Comminuting  effects — Co-opera- 
tion with  saliva — Dental  pressures — Effects  of  mastication  on  later 
digestive  processes  8 — II 

Movements  of  deglutition :  Discharge  theory  of  swallowing — Movements 
of  the  mouth  parts — Pressure  developed — Experiments  of  Kronecker 
and  Meltzer — X-ray  observations  of  deglutition  in  various  animals — 
Differences  with  different  consistencies  of  food  -  -  11 — 19 

CHAPTER  III 
THE  NERVOUS  CONTROL  OF  DEGLUTITION 

Histological  basis  for  the  observed  variations  in  deglutition — Sensory 
areas  for  deglutition — Nervous  control  of  buccal  and  pharyngeal 
muscles — Innervation  of  the  oesophagus — Two  ways  by  which  the  ^0? 
vagi  effect  oesophageal  peristalsis  ;  primary  and  secondary  peristalsis 
— Effect  of  vagus  section — A  tertiary  peristalsis  -        20 — 31 

CHAPTER  IV 
CONDITIONS  AFFECTING  THE  ACTIVITIES  OF  THE  CARDIA 

Nature  of  the  cardia — Normal  state — Degree  of  tonicity — Action  after 
deglutition — Nervous  control — Effects  of  vagus  section — Spasm  of 
the  sphincter — Rhythmic  oscillations  of  contraction  and  relaxation 
—Effects  of  acid  in  the  stomach — Regurgitation  of  gastric  contents 
in  man  -  -  32 — 44 

vii 


Vlll  CONTENTS 

CHAPTER  V 
THE  MOVEMENTS  OF  THE  STOMACH 

Nature  of  the  gastric  reservoir — Its  relation  to  the  activities  of  the  small 
intestine — Anatomy  of  the  stomach:  its  musculature — Position  of 
the  normal  stomach,  and  the  question  of  gravity  drainage — Change 
in  shape  of  stomach  during  digestion — Peristalsis  of  the  gastric  tube 
— Function  of  the  cardiac  sac — Two  views  of  gastric  peristalsis,  with 
reference  to  the  pyloric  vestibule — Functions  of  the  vestibule  to 
churn  and  expel  the  chyme- -Rate  of  gastric  peristalsis,  and 
conditions  affecting  it  -  -  .  45 53 

CHAPTER  VI 
THE  EFFECTS  OF  STOMACH  MOVEMENTS  ON  THE  CONTENTS 

Adaptation  of  the  stomach  to  a  changing  amount  of  contents  without 
change  of  pressure — Intragastric  pressure :  different  in  the  cardiac 
and  pyloric  ends — Theory  of  the  circulation  of  gastric  contents — 
X-ray  observations  of  the  motions  of  the  food — Churning  of  the 
food  in  the  pyloric  end — Immobility  of  the  food  in  the  cardiac  sac — 
Superficial  digestion  of  this  food — Application  to  man — Churning 
mechanism  in  the  pyloric  vestibule — Importance  of  this  mechanism 
for  admixing  gastric  juice,  continuing  gastric  secretion,  promoting 
absorption,  triturating  and  expelling  chyme  -  -  59 — 70 


CHAPTER  VII 

THE  STOMACH  .MOVEMENTS  IN  RELATION  TO    SALIVARY 
DIGESTION,  AND  GASTRO-ENTEROSTOMY 

Salivary  digestion  in  the  stomach :  Conditions  in  the  cardiac  end  of  the 
stomach  favourable — Difference  in  sugar  percentage  in  two  ends  of 
the  stomach — Effect  of  giving  liquid  food,  and  small  amounts — 
Importance  of  salivary  digestion  -  71 — 74 

Movement  of  food  after  gastro  -  enterostomy :  Futility  of  gastro- 
enterostomy  as  a  drainage  operation — Food  near  pylorus  more  fluid 
and  under  more  pressure  than  elsewhere  in  the  stomach — Food 
leaves  by  the  pylorus  rather  than  by  stoma  even  if  pylorus  narrowed 
— Conditions  for  circulation  of  food — Obstructive  kinks  of  the  gut, 
and  means  of  avoiding  them — Compensation  for  disturbed  course 
of  the  food — Superiority  of  pyloroplasty  74 — 83 


CHAPTER  VIII 

THE  PASSAGE  OF  DIFFERENT  FOODSTUFFS  FROM  THE 
STOMACH 

X-ray  method  of  studying  gastric  discharge — Consideration  of  defects  of 
the  method — Objections  to  other  methods — The  discharge  of  fats — 
The  discharge  of  carbohydrates — The  discharge  of  proteins — Com- 
parison of  the  carbohydrate  and  protein  discharge — The  discharge 


CONTENTS  IX 

PAGES 

when  carbohydrate  or  protein  is  fed  first,  and  the  other  second — 
The  discharge  when  mixtures  are  fed  :  protein-fat,  carbohydrate- 
protein,  carbohydrate-fat  -  84 — 95 

CHAPTER  IX 
THE  ACID  CONTROL  OF  THE  PYLORUS 

Stomach  emptied  progressively  by  occasional  opening  of  the  pylorus — 
Inadequate  explanation  by  mechanical  conditions  in  stomach  or 
intestine — Explanation  by  chemical  conditions — The  failure  to 
recognize  the  two  factors  concerned  in  gastric  discharge — The  facts 
to  be  explained — Theory  of  the  control  of  the  pylorus  by  opposite 
action  of  acid  above  and  below — Evidence  that  acid  in  the  vestibule 
opens  the  pylorus,  and  in  the  duodenum  keeps  the  pylorus  closed  96—111 

CHAPTER  X 

THE  CORRELATING  FUNCTIONS  OF  THE  PYLORUS,  AND 
SOME  CONDITIONS  AFFECTING  IT 

Importance  of  the  pylorus  in  correlating  gastric  and  intestinal  secretory 
and  digestive  processes — Explanation  of  the  differential  discharge  of 
the  different  foodstuffs — The  peculiar  discharge  of  fats — Passage  of 
water  through  the  stomach — The  discharge  of  egg-white — Influence 
of  hyperacidity  on  gastric  discharge — Influence  of  consistency  of 
food  ;  of  the  presence  of  hard  particles — Influence  of  gas  in  the 
stomach — Influence  of  heat  and  cold — The  effects  of  some  patho- 
logical conditions  ;  intestinal  injury,  irritation  of  the  colon,  absence 
of  gastric  secretion  -  112 — 129 

CHAPTER  XI 
THE  MOVEMENTS  OF  THE  SMALL  INTESTINE 

Importance  of  the  small  intestine — Co-operation  of  mechanical  factors — 
Rhythmic  segmentation ;  various  types,  occurrence  in  different 
animals,  functions,  its  relation  to  "  pendulum  movements " — 
Peristalsis  ;  nature  of  the  peristaltic  wave,  combined  peristalsis  and 
segmentation — Relation  of  peristalsis  to  end-to-end  and  lateral 
intestinal  union — Peristalsis  in  the  presence  of  intestinal  obstruction 
— Question  of  antiperistalsis — Peristaltic  rush  ;  its  probable  function 
— Course  of  food  in  the  small  intestine — Rate  of  passage  of  different 
foodstuffs  through  the  small  intestine  -  -  130 — 147 


CHAPTER  XII 
THE  MOVEMENTS  OF  THE  LARGE  INTESTINE 

Relations  of  stomach  and  caecum  in  herbivores — Functions  of  the  caecum 
and  proximal  colon — Antiperistalsis  in  the  proximal  colon  (cat) — • 
The  changes  when  food  enters  the  colon — Antiperistalsis  of  the  colon 


CONTENTS 

PAGES 

in  other  animals  than  the  cat — The  question  of  antiperistalsis  in  the 
human  large  intestine — Antiperistalsis  with  reference  to  the  ileo- 
colic  sphincter,  with  reference  to  the  passage  of  material  from  colon 
to  ileum — The  distal  colon ;  tonic  constrictions — Movement  of  the 
contents — Defaecation — Conditions  preceding  the  act  in  man  -  148 — 163 


CHAPTER  XIII 
AUSCULTATION  OF  CASTRO-INTESTINAL  SOUNDS 

Early  observations  on  alimentary  sounds — Rhythmicity  characteristic 
of  the  movements  of  the  canal — Method  of  recording  sounds — Sounds 
produced  by  the  stomach — Sounds  produced  by  the  small  intestine 
— Sounds  produced  by  the  large  intestine — Other  auscultatory 
observations — Use  of  the  method  -  164 — 17 

CHAPTER  XIV 

THE  INTRINSIC  INNERVATION  OF  THE  GASTRO- 
INTESTINAL TRACT 

Nature  of  peristalsis  in  the  small  intestine — Evidence  of  local  control — 
The  "law  of  the  intestine"  :  contraction  above,  relaxation  below,  a 
stimulated  point — Nature  of  the  rhythmic  contractions — Their 
dependence  on  nervous  connections — Importance  of  the  refractory 
period  for  the  rhythm — Conditions  governing  peristalsis  and 
rhythmic  contraction  -  -  178 — 185 

Peristalsis  and  antiperistalsis  in  the  large  intestine — The  local  reflex — 
Nature  of  antiperistalsis — Origin  of  antiperistaltic  waves  in  a 
pulsating  tonus  ring — Relation  to  internal  pressure  -  -  185 — 190 

Nature  of  gastric  peristalsis — Similarity  to  antiperistalsis  of  the  colon — 
Explanation  of  gastric  waves  by  experimental  conditions  in  the 
large  intestine — Gastric  antiperistalsis  -  -  190 — 194 

Myenteric  reflex — Its  presence  throughout  the  alimentary  canal — Co- 
existence with  other  waves  moving  forward  or  back — Importance  of 
the  tonic  state  for  these  waves  -  -  194 — 196 

CHAPTER  XV 

|,'THE  EXTRINSIC  INNERVATION  OF  THE  GASTRO- 
INTESTINAL TRACT  j 

Origins  of  the  extrinsic  nerves — Innervation  of  the  stomach — Effects  of 
vagus  stimulation — Immediate  atony  after  vagus  section,  and  later 
recovery — Nature  of  vagus  action — Psychic  tonus — Ineffectiveness 
of  vagus  section  during  digestion — Receptive  relaxation  of  the 
stomach — Inhibition  of  gastric  tonus  by  splanchnic  influences— The 
question  of  sensations  arising  in  the  stomach ;  visceral  pain — 
Hunger  -  197—204 

Extrinsic  innervation  of  the  small  intestine  :  Effects  of  vagus  stimulation 
— Effects  of  splanchnic  stimulation — Effects  of  severing  these  nerves 
— Elimination  of  vascular  influences  -  -  -  204 — 205 


CONTENTS  XI 

Extrinsic  inner vation  of  the  large  intestine :  Lumbar  and  sacral  supply 

— Crossed  innervation — Effects  of  nerve  section — Defalcation  -  205 — 207 

Inner  vation  of  the  sphincters  :  Pylorus  —  Ileo-colic  —  Internal  anal 

sphincter — Rule  of  sympathetic  innervation  -  -  -  207 — 209 


CHAPTEE  XVI 

DEPRESSIVE  NERVOUS  INFLUENCES  AFFECTING  GASTRO- 
INTESTINAL MOVEMENTS 

Influence  of  asthenia  on  gastro-intestinal  movements — Effects  of  nerve 

section  on  the  phenomenon  -  .  210 — 211 

The  nature  of  post-operative  paralysis — Effects  of  etherization,  of 
exposure,  of  cooling,  and  of  manipulation  —  Local  and  reflex 
paralysis — Local  paralysis  from  manipulation — Reflex  paralysis  via 
the  splanchnic  nerves — Importance  of  distinguishing  the  two  sources 
of  inactivity  -  -  211 — 217 

Influence  of  emotional  states — Inhibition  of  gastric  peristalsis  and  of 
intestinal  movements — Course  of  inhibitory  impulses — Importance  of 
mental  states  favourable  and  unfavourable  to  digestion  -  217 — 220 

Publications  from  the  Laboratory  of  Physiology  of  Harvard  University 

bearing  on  the  Mechanical  Factors  of  Digestion  221 

Index  ........  223 


THE    MECHANICAL    FACT 
DIGESTION 


CHAPTER  I 

GENERAL  FEATURES  OF  THE  MOVEMENTS  OF  THE  ALIMENTARY 
CANAL,  AND  METHODS  OF  INVESTIGATION 

SINCE  the  digestive  tube  is  an  enfolded  portion  of  the  body 
surface,  food  taken  into  it  is  not  in  the  body,  but  is  merely 
enclosed.  The  chief  functions  of  digestion  are  to  render  the 
food  serviceable,  and  to  give  it  a  consistency  suitable  for  passage 
through  the  wall  of  the  tube  into  the  body.  The  region  in  which 
occur  the  final  preparations  for  entrance  of  the  food  into  the 
body  is  the  small  intestine.  There  the  enzymes  are  found  that 
finish  the  work  begun  by  the  enzymes  of  the  mouth  and  stomach. 
In  the  small  intestine  also  the  digested  material  is  mainly 
absorbed.  Indeed,  this  long,  narrow  portion  of  the  alimentary 
tract  may  rightly  be  regarded  as  the  very  centre  of  digestive 
and  absorptive  activity,  with  a  preparatory  reservoir,  the 
stomach,  containing  accumulated  food,  which  it  delivers  gradually 
to  the  small  intestine,  and  with  a  terminal  reservoir,  the  colon, 
ready  to  receive  accumulating  waste. 

The  two  general  factors  of  digestion,  the  chemical  and  the 
mechanical,  which  work  towards  the  absorption  of  the  food,  are 
intimately  interrelated.  Although  our  consideration  of  the 
activities  of  the  canal  will  lay  emphasis  on  the  mechanical 
factors,  we  must  not  fail  to  keep  in  mind  the  chemical  agencies 
which  they  accompany  and  with  which  they  co-operate.  The 
mechanical  factors  have  the  functions  of  mixing  the  food  with 
the  secretions  poured  out  upon  it,  of  exposing  the  digested  food 
to  the  absorptive  wall,  of  propelling  the  food  from  one  region  of 
digestion  or  absorption  to  another,  and  finally  of  discharging  the 
waste.  These  functions  are  of  great  import  to  the  body,  for  the 

1 


2  THE   MECHANICAL   FACTORS    OF   DIGESTION 

food,  if  conducted  too  slowly  along  the  tube,  may  suffer  harmful 
decomposition ;  and  if  forced  on  too  rapidly,  it  will  fail  to  be 
properly  digested,  and  will  in  large  measure  be  lost.  We  may 
expect  to  find,  therefore,  that  the  rate  of  passage  through  the 
different  parts  of  the  tube  is  nicely  adapted  to  the  speed  of  the 
chemical  changes. 

The  neuro-muscular  structures  by  which  the  mechanical 
functions  of  digestion  are  performed  are  singularly  uniform 
throughout  the  tube.  They  consist  of  two  muscular  coats — 
the  circular  coat  nearer  the  lumen  of  the  tube,  and  the  outer 
longitudinal  coat.  The  latter  may  be  lacking  in  small  areas, 
especially  in  the  region  of  the  stomach.  Between  these  two 
muscular  layers  is  a  primitive  nerve  plexus — Auerbach's — or  the 
myenteric  plexus.  At  the  beginning  of  the  tube,  and  at  its  end, 
striped  muscle  prevails,  but  except  at  these  extremities  the 
musculature  is  of  the  smooth  variety.  Smooth  muscle  is  charac- 
terized by  the  relative  slowness  and  the  rhythmicity  of  its  con- 
tractions, and  by  its  ability  to  exhibit  rhythmic  activities  at 
various  levels  of  sustained  shortening,  or  tonus.  The  great 
importance  of  these  characteristics  will  appear  as  we  consider 
further  the  functions  that  are  performed  by  this  smooth  muscle 
and  its  nerve  plexus. 

In  accordance  with  uniformity  of  neuro-muscular  structure, 
the  canal  presents  uniformity  of  mechanical  action.  In  the 
course  of  digestion  the  food  is  subjected  to  an  orderly  series  of 
sequentially  related  processes ;  what  occurs  in  an  advanced 
region  is  more  or  less  dependent  on  what  has  occurred  in  a 
region  previously  traversed.  The  food,  therefore,  must  be  moved 
always  onward.  The  continued  progress  of  the  food  is  accom- 
plished in  the  main  by  peristaltic  waves — rings  of  constriction 
which  sweep  slowly  along  limited  extents  of  the  canal.  These 
waves  are  an  expression  of  the  neuro-muscular  arrangements  in 
the  wall.  Although,  as  we  shall  see,  the  peristalsis  of  the 
stomach  and  proximal  colon  is  somewhat  different  from  that  of 
the  small  intestine,  we  need  not  restrict  the  term  to  any  particular 
region.  In  all  parts  of  the  canal,  therefore,  peristalsis  is  the 
most  characteristic  mechanical  activity  that  affects  the  digestive 
processes. 

The  manner  in  which  peristalsis  operates  varies  in  different 
parts.  Where  digestive  juices  are  lacking  and  absorption  does 
not  occur,  as  in  the  oesophagus,  the  waves  press  the  food  onward 


MOVEMENTS    OF   THE    ALIMENTARY    CANAL  3 

with  rapidity.  On  the  other  hand,  where  digestion  and  absorp- 
tion can  take  place,  rapid  progression  is  prevented  by  sphincters  ; 
and  the  recurring  peristaltic  waves  passing  over  the  food  toward 
closed  sphincters  serve  to  mix  the  food  with  the  digestive  juices, 
as  in  the  stomach,  or  to  expose  the  food  to  the  absorbing  mucosa, 
as  in  the  ascending  colon.  In  the  long  course  of  the  small 
intestine,  where  there  are  no  sphincters  to  oppose  peristalsis, 
peristaltic  activity  is  less  noteworthy  than  in  the  other  regions, 
and  the  mixing  and  churning  functions  are  performed  by  a  special 
method — the  rhythmic  contraction  of  the  circular  fibres  which 
knead  the  intestinal  contents  without  causing  any  considerable 
progression.  The  advancement  of  the  contents  in  the  small 
intestine,  however,  is  effected  by  the  peristaltic  wave.  In  all 
regions  of  the  digestive  tube,  therefore,  this  wave  is  to  be  seen 
as  the  means  of  conveyance. 

The  muscles  at  the  beginning  and  at  the  end  of  the  canal  are 
under  voluntary  control.  Thus  we  can  determine  what  food 
shall  be  taken  into  the  tube,  and  when,  and  we  can,  within  limits, 
govern  the  discharge  from  the  tube.  The  great  mid-region, 
however,  is  normally  automatic,  and  free  from  voluntary  inter- 
ference. The  active  stomach,  for  example,  can  be  removed 
from  the  body  and  placed  in  a  moist  chamber,  where  its  contrac- 
tions will  continue  for  an  hour  or  more.  These  automatic 
structures  are,  nevertheless,  subject  to  influences  from  the 
central  nervous  system  which  augment  or  diminish  their  inherent 
activity.  The  important  relations  which  exist  between  the 
alimentary  tract  and  the  central  nervous  system  have  only 
recently  been  ascertained,  as  new  methods  of  research  have  brought 
forth  the  clear  evidence.  We  shall  see  that  disturbances  arise 
if  the  extrinsic  innervation  is  removed,  and  that  disturbances 
may  arise  also  because  the  extrinsic  innervation  is  present. 

The  sensitiveness  of  the  alimentary  canal  to  operative  inter- 
ference has  been  the  chief  difficulty  in  past  investigations  of 
the  digestive  process.  The  stomach  and  intestines,  energetically 
active  during  the  height  of  digestion,  are  prone  to  cease  their 
activities  suddenly  when  the  abdomen  is  opened,  a  striking 
change,  likened  by  Meltzer  to  the  hush  that  falls  upon  a  company 
when  a  stranger  appears  at  the  door.  Of  course,  under  these 
circumstances  the  normal  movements  of  the  canal  cannot  be 
studied.  The  famous  physiologist,  Johannes  Miiller,  testified 
that  he  had  never  seen  clearly  the  peristaltic  movements  of  the 


THE   MECHANICAL   FACTORS    OF   DIGESTION 

stomach.  For  centuries  the  priests  and  the  butchers,  who 
watched  the  entrails  of  their  sacrificed  victims,  knew  as  much  as 
the  physicians  about  the  mechanical  factors  of  digestion.  Only 
as  methods  were  devised  which  maintained  more  or  less  perfectly 
the  normal  conditions  of  the  digestive  organs  were  the  natural 
activities  slowly  ascertained. 

Among  the  methods  employed  to  preserve  so  far  as  possible, 
or  to  simulate  during  investigation,  the  usual  surroundings  of 
the  alimentary  canal,  the  fistula  is  the  oldest.  Through  an 
opening  between  the  lumen  of  the  canal  and  the  body  surface, 
registering  apparatus  has  been  introduced  which  indicated  the 
movements  of  the  region.  Fistulas  made  at  different  distances 
along  the  tube  have  also  been  used  to  study  the  rate  of  advance- 
ment of  the  food  and  the  degree  of  its  alteration  as  it  passed  from 
one  stage  to  another  in  digestion.  At  best,  however,  the  fistula 
permits  only  an  inferential  judgment  of  the  mechanical  agencies 
at  work  in  a  narrowly  localized  portion  of  the  canal,  a  portion, 
furthermore,  which  may  be  disturbed  by  the  adhesions  due  to 
operation. 

Less  disturbing  than  the  fistula  method  is  the  direct  intro- 
duction of  registering  apparatus  through  the  mouth.  Thus  the 
time  relations  of  changes  of  pressure  in  the  pharynx,  the  oesoph- 
agus, and  the  two  ends  of  the  stomach,  have  been  obtained, 
and  conclusions  have  been  drawn  as  to  the  activities  that  pro- 
duced the  pressures. 

A  method  giving  more  direct  information  than  either  of  the 
foregoing  methods  is  that  introduced  by  v.  Braam-Houckgeest,1 
which  consisted  in  opening  the  abdominal  cavity  of  the  anesthe- 
tized animal  in  a  bath  of  physiological  salt  solution  at  body 
temperature.  If  the  temperature  of  the  solution  is  sustained 
and  active  digestion  is  in  process,  the  normal  movements  of 
the  stomach  and  intestines  can  be  directly  observed.  The 
method  involves  such  serious  operative  interference,  however, 
that  with  some  animals  (e.g.,  the  rabbit2)  the  usual  gastric  peri- 
stalsis suffers  profound  and  lasting  nhibition.  The  effects  of 
the  movements  on  the  food,  and  the  rate  at  which  the  food  is 
advanced,  cannot  be  readily  ascertained  in  the  salt  bath. 

All  physiological  processes  observed  under  conditions  rendered 
unnatural  by  the  exigencies  of  the  method  employed  must  be 
subject  to  standardization  by  the  results  of  studies  made  under 
more  natural  conditions.  None  of  the  methods  above  described 


MOVEMENTS    OF   THE    ALIMENTARY    CANAL  5 

preserve  strictly  the  normal  state  of  an  animal  digesting  its  food 
in  its  usual  manner.  When  the  X  rays  were  discovered,  a  new 
means  of  investigating  the  alimentary  tract  was  provided,  which 
permitted  observations  to  be  made  without  interfering  with 
the  animal  to  any  disturbing  degree.  This  means  of  research 
was  suggested  to  me,  when  a  medical  student,  by  my  teacher 
of  physiology,  Professor  H.  P.  Bowditch,  in  the  autumn  of 
1896.  The  results  obtained  by  use  of  the  X  rays  prove  that, 
in  order  to  reveal  the  natural  activities  of  the  digestive  organs, 
the  older  methods  must  be  used  with  extreme  care.  When  such 
care  is  exercised,  however,  those  methods  can  be  safely  employed 
to  confirm  and  supplement  the  X-ray  observations.  Most  of 
the  data  which  will  be  hereafter  presented  have  been  secured 
by  study  of  the  deeply  hidden  alimentary  canal  by  means  of 
the  X  rays. 

The  method  consisted  in  giving  animals  food  thoroughly 
mixed  with  subnitrate  of  bismuth,*  and  observing  the  shadows 
cast  by  the  X  rays  on  a  fluorescent  screen.  Thus  the  dense 
bismuth  powder,  uniformly  mixed  with  the  food  that  fills  the 
stomach,  throws  the  dark  shadow  of  the  stomach  contents  on 
the  screen,  and  the  changes  in  the  shape  of  the  outline  reveal 
the  movements  of  the  organ.  That  the  addition  of  bismuth 
subnitrate  to  the  food  produces  no  peculiar  effects  on  the  move- 
ments has  been  proved  by  finding  no  noteworthy  differences 
when  other  heavy  salts,  as,  for  example,  barium  sulphate,  is 
mixed  with  the  food.3  Clinical  studies  on  man  by  Schule  also 
indicate  that  subnitrate  of  bismuth  in  the  food  does  not  inter- 
fere with  normal  gastric  motility,4  and  observations  by  Cook 
and  Schlesinger  show  that  bismuth  oxychloride  passes  through 
the  digestive  tube  at  the  rate  of  charcoal.5 

The  animal  most  commonly  used  in  the  laboratory  investiga- 
tions was  the  cat.  Confirmatory  observations,  however,  have 
been  made  on  the  dog,  rabbit,  guinea-pig,  white  rat,  and  on 
man.  For  studying  the  conditions  in  the  cat,  deprivation  of 
food  for  twenty-four  or  thirty  hours  previous  to  the  feeding  was 
usually  necessary,  in  order  to  make  certain  that  the  digestive 

*  A  few  of  the  animals  unaccountably  died  after  being  observed.  Cases  of 
death  or  severe  poisoning  in  man  after  the  administration  of  large  doses  of 
subnitrate  of  bismuth  have  been  reported  in  Germany  and  the  United  States. 
As  the  subnitrate  of  bismuth  may  to  some  extent  be  chemically  changed  in  the 
stomach,  Hertz  has  advocated  the  use  of  bismuth  oxychloride,  which  is  un- 
affected by  either  the  gastric  or  the  intestinal  juices.  (See  Hertz,  Contiipithn 
and  Allied  Intestinal  Disorders,  London,  1909,  p.  335.) 


6  THE   MECHANICAL   FACTORS    OF  DIGESTION 

tube  was  empty.  A  dose  of  castor-oil,  administered  about  twelve 
hours  before  the  feeding,  gave  still  further  assurance  that  only 
the  digestion  of  food  mixed  with  the  bismuth  salt  would  be 
observed.  The  animals  were  either  permitted  to  eat  voluntarily 
from  a  dish,  or  were  placed  on  the  animal -holder  and  fed  from 
a  spoon,  usually  with  little  or  no  difficulty.  The  amount  of  food 
given  varied  between  25  and  50  c.c.,  except  where  uniform 
amounts  were  given  for  special  purposes.  One  or  two  grammes 
of  the  bismuth  powder  produced  a  dim  shadow  of  the  stomach 
within  which  could  be  clearly  seen  the  darker  forms  of  any  food 
containing  a  larger  amount  of  the  substance.  Four  or  five 
grammes,  mixed  with  25  c.c.  of  food,  were  needed  to  see  the 
passage  of  the  food  from  the  pylorus. 

The  animal-holder  consisted  of  a  framework  supporting  a 
sheet  of  black  rubber  cloth.  The  frame  was  made  of  two  side- 
pieces,  each  80  centimetres  long  and  2-5  centimetres  square, 
connected  at  either  end  by  blocks  2-5  centimetres  thick, 
12-5  centimetres  wide,  and  16  centimetres  long.  The  rabber 
cloth,  which  sagged  for  the  comfort  of  the  animal,  was  fastened 
by  strips  of  wood  to  the  inner  surface  of  the  frame.  Through  the 
side-pieces  were  holes  0-6  centimetre  in  diameter,  and  5  centi- 
metres apart.  The  legs  of  the  animal  were  secured  by  leather 
nooses  ;  the  leather  passed  down  through  one  of  these  holes  and 
up  through  another,  in  which  it  was  made  fast  byforcing  a  pointed 
peg  into  the  hole  with  it.  The  cat's  head  was  held  by  two 
adjustable  pegs,  one  on  either  side  of  the  neck,  which  were  con- 
nected above.  The  advantage  of  this  holder  lay  in  its  comfort- 
ableness for  the  animal,  and  in  the  ease  of  feeding  which  it  per- 
mitted in  case  artificial  administration  of  food  became  necessary. 

For  seeing  the  regular  movements  of  the  stomach,  the  animal 
was  tied  back  downward,  with  the  fore -paws  in  nooses  at  either 
side,  and  the  hind-legs  stretched  out  and  fastened  to  the  holder 
in  such  manner  as  to  permit  the  body  to  lie  slightly  turned 
towards  the  right  side.  This  position  was  also  favourable  for 
watching  the  course  of  food  through  the  oesophagus.  The 
movements  of  food  in  the  intestines  could  be  readily  observed 
with  the  animal  lying  directly  on  the  back.  Female  cats  lay  on 
the  holder  sometimes  for  periods  of  an  hour  or  more  without 
making  attempts  to  break  away  or  manifesting  signs  of  dis- 
comfort. In  marked  contrast  was  the  behaviour  of  the  male 
cats  ;  almost  without  exception  they  showed  signs  of  anxiety . 


MOVEMENTS    OF  THE   ALIMENTARY   CANAL  7 

or  rage  when  fastened  down.  The  important  effects  on  digestion 
arising  from  these  different  ways  of  reacting  to  the  novel  sur- 
roundings will  be  described  later. 

The  animal-holder  was  supported  on  a  leaden  surface  in  which 
a  hole  was  cut  only  sufficiently  large  to  permit  the  body  of  the 
animal  to  be  illuminated  by  the  X  rays.  Below  the  holder, 
at  a  distance  of  30  centimetres  between  the  anode  and  the 
animal,  was  placed  the  tube  generating  the  rays.  The  tube  was 
so  surrounded  by  lead  that  none  of  the  rays  could  reach  the 
observer.  The  observations  were  conducted  in  a  dark  room. 
All  light  from  the  tube  and  from  the  machine  which  generated 
the  electric  discharge  was  shut  off  from  the  observer  by  drapings 
of  black  cloth.  Thus  in  an  open  fluorescent  screen  placed  on 
the  animal's  belly,  the  shadows  could  be  observed  simultaneously 
by  more  than  one  person.  Over  the  screen  was  fastened  a  layer 
of  lead  glass.  On  transparent  tissue  paper  laid  over  the  glass 
the  outlines  of  the  gastric  and  intestinal  contents  could  be  traced, 
and  thus  records  of  the  conditions  at  various  times  in  the  course 
of  digestion  could  be  preserved.  In  case  of  doubt  as  to  the 
accuracy  of  the  tracings,  an  electric  light  momentarily  flashed 
on  the  tracing  before  the  tissue  paper  was  removed  from  the 
screen  permitted  the  outlines  drawn  on  the  paper  to  be  compared 
with  the  shadows,  and  the  records  thus  verified. 

By  use  of  the  X  rays  the  rate  of  passage  of  food  through  the 
oesophagus,  the  speed  of  gastric  peristalsis  and  its  rhythm,  the 
oscillating  contractions  of  the  small  intestine,  the  peculiar  anti- 
peristalsis  of  the  large  intestine,  the  rapidity  of  discharge  of 
gastric  contents  into  the  duodenum,  the  time  required  for  material 
to  be  carried  to  the  colon,  and  all  the  influences  external  and 
internal  that  affect  these  processes,  can  be  observed  continuously 
for  as  long  a  time  as  the  animal  remains  in  a  state  of  peace  and 
contentment.  The  results  of  these  observations  we  shall  now 
begin  to  consider. 

REFERENCES. 

1  v.  Braam-Houckgeest,  Arch.  /.  d.  Ges.  PhysioL,  1872,  vi.,  p.  203. 

2  See  Auer,  Am.  J.  Physid.,  1907,  xviii.,  p.  359. 

3  Cannon,  Am.  J.  Physid.,  1904,  xii.,  p.  388. 

4  Schule,  Ztschr.  f.  Klin.  Med.,  1896,  xxix.,  p.  07. 

5  Hertz,  loc.  cit.,  p.  335. 


CHAPTEE  II 

THE  MOVEMENTS  OF  MASTICATION  AND  DEGLUTITION 

THE  MOVEMENTS  OF  MASTICATION. 

THE  freedom  of  movement  of  the  lower  jaw  permits  a  wide 
variety  of  relations  between  the  upper  and  lower  rows  of  teeth. 
They  can  be  brought  together,  separated,  or  pressed  with  a 
sliding  motion  one  row  upon  the  other  either  forward  and  back- 
ward or  from  side  to  side.  The  up  and  down  motion  is  essential 
to  the  use  of  the  biting  front-teeth;  the  side  to  side  motion  is 
more  useful  in  the  later  process  of  chewing.  The  tongue  and 
cheeks  act  like  the  hopper  of  a  mill,  and  force  the  food  between 
the  grinding  facets  until  it  is  broken  or  torn  into  fragments  of 
proper  size  for  swallowing. 

The  duration  of  mastication  varies  with  appetite,  with  age, 
the  demands  of  business,  the  quantity  of  food  in  the  mouth, 
and  especially  with  the  nature  of  the  food — whether  fluid  or 
gummy,  moist  or  dry,  crisp  or  tough.  The  amount  of  mastica- 
tion given  any  food  is  related  to  the  readiness  with  which  a  mass 
is  comminuted,  insalivated  and  gathered  into  a  bolus,  and  is 
not  related  to  the  degree  of  salivary  digestion.  Thus  soft,  starchy 
food  is  little  chewed,  whereas  hard  or  dry  food,  not  starchy 
in  nature,  may  require  much  chewing  before  ready  to  be 
swallowed.1 

The  effect  of  the  mechanical  treatment  in  the  mouth  is  the 
production  of  a  semi-fluid  mush  in  which  there  are  likely  to  be 
particles  of  varying  size.  Lehmann  has  reported  that  when  he 
chewed  different  substances,  such  as  beef,  macaroni,  potato, 
and  raw  apple,  until  the  impulse  to  swallow  came,  some  of  the 
substance  was  already  in  solution;  and  of  the  rest,  by  far  the  larger 
amount  was  reduced  to  particles  less  than  2  millimetres  in 
diameter.2  Such  jcomminution  must  result  in  an  enormous 

8 


MASTICATION   AND   DEGLUTITION  9 

increase  in  the  surface  exposed  to  the  action  of  digestive  enzymes, 
and  thereby  promotes  the  rapidity  of  their  action.  The  observa- 
tions of  Lehmann  have  been  confirmed  by  Fermi  and  by  Gaudenz. 
In  the  mushy  mass,  however,  Gaudenz  found3  particles  over 
7  millimetres  in  diameter,  and  he  states  that  the  largest  normally 
swallowed  do  not  exceed  a  diameter  of  12  millimetres.  For 
determining  the  proper  grade  of  fineness  of  the  food,  the  tongue, 
the  teeth,  the  gums  and  cheeks,  make  the  needed  investigation. 
If  some  particles  in  the  bolus  as  it  is  carried  backward  in  the 
mouth  are  too  large,  they  are  returned  for  further  mastication. 

The  secretion  of  saliva,  which  softens  the  hard  particles  in 
the  food,  and  with  its  ptyalin  starts  the  digestion  of  starches, 
is  also  promoted  by  the  movements  of  mastication.  According 
to  Gaudenz,4  the  weight  of  the  material  in  the  mouth  when  ready 
to  be  swallowed  varies  in  man  between  3-2  and  6-5  grammes, 
and  of  this,  if  the  food  has  been  chewed  for  twenty  or  thirty 
seconds,  1  or  1-5  grammes  may  be  saliva. 

The  mass  suitable  for  normal  mastication  has  an  average 
volume  of  about  5  c.c.  Not  all  animals  chew  the  food  as  finely 
as  man  commonly  chews  it.  The  dog  and  cat  swallow  pieces 
of  meat  so  large  that  apparently  the  oesophagus  must  have 
difficulty  in  conveying  them,  and  yet  these  animals  seem  to  have 
no  instinct  to  divide  this  food  into  smaller  and  more  readily 
manipulated  fragments.  The  large  lumps  are  merely  moved 
about  in  the  mouth  until  they  are  coated. with  saliva,  and  are 
then  forced  backward  into  the  gullet.  In  man,  also,  food  may 
be  swallowed  in  such  haste  that  it  is  barely  covered  with  the 
saliva  which  usually  lubricates  the  passage  through  the  oesoph- 
agus. Masses  10  or  12  millimetres  in  diameter  may  thus 
enter  the  stomach  with  little  evidence  that  the  teeth  have  in 
any  way  affected  them.  The  ability  to  bolt  food  in  unbroken 
masses  can  doubtless  be  cultivated  ;  and  a  person  who  has  made 
himself  an  expert  in  this  act  can  probably  push  downward  bigger 
masses  than  those  just  mentioned. 

The  pressure  exerted  in  the  process  of  mastication  may  be  / 
surprisingly  great.  The  pressure  which  the  molars,  for  example, 
are  capable  of  exerting,  as  determined  by  a  spring  dynamometer, 
may  be  as  high  as  270  pounds.5  With  a  direct  thrust  the  crush- 
ing-point of  cooked  meats  has  been  found  to  vary  between 
15  and  80  pounds  ;  of  candies,  between  30  and  110  pounds  ;  and 
of  various  kinds  of  nuts,  between  55  and  170  pounds.  The  figures 


10  THE   MECHANICAL   FACTORS    OF  DIGESTION 

for  meats  may  be  considerably  less  if  the  jaws  grind  from  side 
to  side.  The  teeth  then  bite  through  cooked  tongue  when  the 
pressure  is  only  1  or  2  pounds,  and  through  tough  round  of  beef 
when  the  pressure  is  about  40  pounds.  Saliva  is  a  further  aid 
to  mastication  if  starchy  food  is  being  chewed.  Thus  soft  bread 
is  not  bitten  through  even  with  60  pounds  direct  pressure,  but 
hardens  to  a  solid  mass.  If  the  bread  is  softened  with  a  little 
saliva,  it  is  easily  masticated  with  a  pressure  of  3  pounds.6 
Before  the  saliva  is  well  mixed  with  the  food,  however,  the  high 
pressure  may  have  to  be  applied  a  large  number  of  times  to- 

X^reduce  the  mass  to  bits. 

Breaking  the  food  into  fine  fragments  and  mixing  it  thoroughly 
with  saliva,  so  that  it  might  be  sufficiently  moist  to  be  swallowed, 
were  formerly  regarded  as  the  most  important  results  of  mastica- 
tion. Recent  researches  have  revealed  less  obvious  results. 
The  voluntary  act  of  chewing  has  been  found  to  have  much 
significance  for  the  proper  initiation  of  gastric  digestion.  During 
mastication  substances  of  pleasant  taste  are  brought  in  contact 
with  the  gustatory  organs  of  the  tongue  and  cheeks,  and  odours 
released  from  the  separated  food  rise  to  the  olfactory  region  of 
the  nose,  and  through  the  pleasurable  sensations  aroused  by 

.  these  stimulations  the  gastric  juice  is  reflexly  started  flowing, 
in  preparation  for  gastric  digestion.7  Not  only  in  laboratory 
animals,  but  also  in  human  beings,  this  remote  effect  of  pleasurable 
sensation  in  the  taking  of  the  food  has  been  demonstrated. 
Hornborg  and  others  have  reported  cases  of  gastric  fistula  in 
children,  in  whom  an  active  secretion  of  gastric  juice  was  observed 
when  agreeable  food  was  chewed,  whereas  the  chewing  of  in- 
different material  was  without  influence.8  As  has  been  proved 
by  the  experiments  of  Pawlow  and  Edkins,  this  initial  "  psychic 
juice  "  may  be  a  prime  condition  for  continuance  of  gastric 
secretion.  We  shall  see  that  it  may  also  be  the  prime  con- 
dition for  the  co-ordination  of  gastric  and  intestinal  digestive 
proceses. 

Still  another  remote  effect  which  may  result  from  the  chewing 
of  agreeable  food  is  the  development  in  the  stomach  of  a  con- 
dition of  tonic  contraction,  a  state  of  sustained  shortening  of 
the  circular  muscles  which  nicely  adapts  the  capacity  of  the 
organ  to  the  contents,  whatever  the  amount  swallowed.  The 
peristalsis  of  the  stomach,  which  churns  the  food  with  the  gastric 
juice  and  pushes  the  chyme  onward  into  the  duodenum,  is 


MASTICATION   AND   DEGLUTITION  11 

dependent  on  the  tension  developed  in  the  muscular  wall  as  a 
result  of  its  tonic  state. 

Although  these  secretory  and  motor  activities  of  the  stomach 
are  not,  as  we  are  aware,  directly  subject  to  voluntary  control, 
they  are  capable  of  being  profoundly  influenced,  favourably  or 
unfavourably,  by  the  character  of  the  experiences,  agreeable  or 
disagreeable,  that  attend  the  process  of  mastication.  And  these 
experiences  we  can  to  some  extent  determine  for  ourselves. 

THE  MOVEMENTS  OF  DEGLUTITION. 

The  movements  of  deglutition,  in  common  with  many  other 
physiological  processes,  were  explained  by  the  older  physiolo- 
gists on  anatomical  grounds.  Thus,  Magendie9  divided  the  act 
into  three  parts,  corresponding  to  the  anatomical  regions  of  the 
mouth,  pharynx,  and  oesophagus.  The  muscles  of  each  of  these 
divisions  were  regarded  as  the  active  agents  in  propelling  the 
food  onward. 

The  function  of  moving  the  mass  to  the  pharynx  was  variously 
ascribed  to  the  tongue  itself,  to  the  mylo-hyoid  muscles  swung 
beneath  the  tongue,  and  to  gravity.  For  the  action  of  the  second 
part,  the  movements  of  the  pharynx,  there  was  more  unanimity 
of  opinion,  since  the  constrictors,  especially  the  middle  and 
lower,  were  evidently  concerned.  The  passage  of  a  swallowed 
mass  along  the  oesophagus  was,  until  1880,  ascribed  solely  to 
peristalsis.  In  that  year,  Falk  and  Kronecker,10  who  had 
studied  the  movements  of  the  mouth  and  pharynx  in  degluti- 
tion, advanced  the  theory  that  the  act  is  accomplished  by 
the  rapid  contraction  of  the  muscles  of  the  mouth,  and  that 
cesophageal  peristalsis  is  of  secondary  importance. 

The  sudden  discharge  involved  in  Falk  and  Kronecker's 
theory  requires  the  temporary  closure  of  all  the  exits  from  the 
mouth  except  that  into  the  oesophagus.  That  there  is  such  a 
closure  anyone  can  observe  to  some  extent  in  himself.  When 
the  food  has  been  sufficiently  masticated,  it  is  gathered  in  a 
depression  on  the  dorsum  of  the  tongue,  in  readiness  for  swallow- 
ing. The  tip  and  sides  of  the  tongue,  pressed  against  the  teeth 
and  hard  palate,  shut  off  the  possibility  of  escape  forward  and 
laterally — we  can  swallow  with  the  mouth  open,  but  not  with 
the  tongue  relaxed.  Since  the  paths  of  respiration  and  degluti- 
tion cross  just  above  the  larynx,  respiration  is  now  reflexly 


12  THE   MECHANICAL  FACTORS    OF  DIGESTION 

stopped.  A  quick  contraction  of  the  mylo-hyoid  muscles 
suddenly  presses  the  tongue  upward  against  the  hard  palate, 
and  by  a  contraction  of  the  hyo-glossus  the  organ  is  drawn 
backwards.  At  the  same  time,  by  action  of  the  palato- 
pharyngeus  muscles,  which  form  the  posterior  pillars  of  the 
fauces,  the  pharynx  is  drawn  to  a  narrow  cleft,  and  against 
this  narrow  opening  the  soft  palate  is  pulled  by  contraction  of 
the  levator  palati.11  Thus  exit  into  the  naso-pharynx  is  pre- 
vented. 

Now,  as  the  tongue  rises  and  slips  inward,  it  acts  as  a  piston, 
and  drives  the  bolus  first  against  the  downward-sloping  soft 
palate,  next  against  the  back  wall  of  the  pharynx,  then  on 
between  the  pharyngeal  wall  and  the  posterior  surface  of  the 
epiglottis,  the  tip  of  which  lies  in  contact  with  the  tongue's 
base.12  Thus  far  the  top  of  the  oesophagus  has  been  kept 
closed  by  pressure  of  the  larynx  against  it.  Immediately  the 
hyoid  bone  and  the  larynx  are  lifted  and  brought  together, 
and  the  epiglottis  is  pressed  back  till  it  shuts  the  laryngeal 
aperture.  As  soon  as  the  hyoid  and  larynx  are  lifted  they  are 
pulled  forward,  and  thus  the  oesophagus  is  opened.  Meanwhile 
the  tip  of  the  epiglottis  slips  downward  along  the  back  wall  of 
the  pharynx,  pushing  the  bolus,  probably  with  a  final  quick 
impulse,  into  the  gullet.  Then  all  the  structures  return  to  their 
resting  posit  ons.  Of  course,  this  sequence  of  movements 
occurs  with  precipitate  suddenness,  and  can  be  known  only  by 
most  careful  analysis. 

Falk  and  Kronecker  found  that  during  the  initiation  of  the 
act  of  swallowing  the  closed  buccal  cavity  showed  a  manometric 
pressure  of  20  centimetres  of  water.  They  found  that  the  same 
pressure  appeared  also  in  the  oesophagus,  but  not  in  the  stomach. 
The  pressure  developed  in  the  mouth  was  considered  sufficient, 
therefore,  to  force  food  quite  through  the  oesophagus  without 
the  aid  of  peristalsis.  Confirmatory  evidence  for  the  theory 
that  the  descent  to  the  stomach  is  rapid  was  found  in  the  common 
experience  that  cold  water  can  be  felt  in  the  epigastric  region 
almost  immediately  after  being  swallowed.  And,  further, 
autopsies  have  shown  that,  when  strong  acids  pass  through  the 
gullet,  they  corrode  areas  only  here  and  there,  and  not  the  entire 
mucous  membrane,  as  would  be  the  case  were  the  acid  pressed 
slowly  to  the  stomach  by  peristalsis. 
During  the  same  year,  in  confirmation  of  the  above  results, 


MASTICATION   AND   DEGLUTITION  13 

the  well-known  experiments  of  Kronecker  and  Meltzer13  were 
reported.  A  rubber  balloon,  connected  by  a  tube  to  a  recording 
tambour,  was  placed  in  the  pharynx,  and  another  balloon, 
similarly  connected,  was  introduced  a  varying  distance  into  the 
oesophagus.  When  water  was  swallowed,  the  increased  pressure 
on  the  pharyngeal  balloon  was  instantly  transmitted  to  the 
first  tambour,  which  recorded  a  rising  curve  on  a  rotating  drum. 
Almost  immediately  thereafter  the  cesophageal  balloon  was 
compressed,  and  its  tambour  recorded  a  curve  below  the  first. 
After  a  varying  number  of  seconds,  according  to  the  distance 
below  the  pharynx  at  which  the  balloon  was  placed,  a  second 
rise  of  pressure  in  the  oesophagus  was  registered.  The  first 
indication  of  increased  cesophageal  pressure  was  explained  as 
due  to  the  sudden  discharge  of  food  past  the  balloon  ;  the  second 
curve  was  explained  as  due  to  a  peristaltic  wave  which  swept 
more  slowly  along  the  tube. 

To  demonstrate  that  the  first  rise  of  pressure  registered  from 
the  oesophagus  resulted  from  the  rapid  squirting  of  liquid  from 
the  mouth,  Meltzer  devised  another  experiment.  A  strip  of 
blue  litmus-paper  was  placed  opposite  the  side  openings  at  the 
lower  end  of  a  stomach-tube.  Attached  to  the  paper  was  a 
thread  which  ran  through  the  tube  to  the  upper  end.  The 
tube  was  now  passed  into  the  lower  end  of  the  oesophagus, 
and  an  acid  drink  swallowed.  If  only  a  half-second  elapsed 
after  the  beginning  of  deglutition,  the  litmus-paper,  when 
pulled  away  from  the  side  openings,  was  found  reddened  by  the 
acid. 

From  these  observations,  Kronecker  and  Meltzer  concluded 
that  liquids  and  semi-solids  are  not  conveyed  down  the  oesoph- 
agus by  peristalsis,  but  are  forcibly  squirted  into  the  stomach, 
by  the  rapid  contraction  of  the  muscles  of  the  mouth,  before  the 
muscles  of  the  pharynx  or  the  oesophagus  have  had  time  to 
contract.  For  this  purpose  the  mylo-hyoids  alone  are  sufficient, 
since  the  middle  and  inferior  constrictors  of  the  pharynx  can  be 
sectioned  without  in  the  least  interfering  with  the  act.  Indeed, 
Meltzer  has  recently  shown14  that  the  musculature  of  the  entire 
cervical  oesophagus  can  be  wholly  removed  from  a  dog,  and 
that  the  animal  thereafter  is  able  to  drink  milk  and  water  quite 
normally  even  when  the  bowl  is  placed  on  the  floor,  and  the 
fluid  must  be  forced  into  the  thoracic  oesophagus  against  gravity. 
If  the  function  of  swallowing  can  thus  be  performed  by  the 


14  THE   MECHANICAL   FACTORS    OF   DIGESTION 

pressure  developed  in  the  mouth,  the  succeeding  peristaltic 
wave  is  of  use  merely  to  gather  any  fragments  that  may  have 
adhered  to  the  wall  in  the  rush  of  food  through  the  oesophagus, 
and  to  carry  this  meagre  load  to  the  stomach. 

According  to  Kronecker  and  Meltzer,15  the  human  oesophagus 
may  be  divided  functionally  into  three  parts  :  a  cervical  part 
6  centimetres  long,  a  middle  part  10  centimetres  long,  and  the 
lowest  part  of  uncertain  length.  These  three  parts  contract 
in  succession,  1-2,  3  and  6  seconds  respectively,  after  degluti- 
tion begins ;  but  each  part,  according  to  Meltzer,  contracts  as 
a  unit,  simultaneously  throughout  its  length.  The  duration 
of  the  contraction  is  more  prolonged  in  the  lower  thoracic  section 
than  in  the  upper  thoracic  or  the  cervical  section.  The  human 
oesophagus,  according  to  this  view,  would  undergo  three  pro- 
gressive sectional  contractions  not  peristaltic  in  nature. 

To  determine  whether  the  cardiac  sphincter  offered  any 
resistance  to  a  rapid  passage  of  food  into  the  stomach,  Meltzer 
made  use  of  another  method.16  If  a  stethoscope  is  placed  over 
the  epigastrium  during  the  swallowing  of  liquids,  a  sound  can 
be  heard  six  or  seven  seconds  after  the  rise  of  the  larynx.  The 
sound  is  ascribed  to  the  passage  of  the  swallowed  mass,  liquid, 
and  air,  through  the  tonically  contracted  cardia.  In  a  few  cases 
a  sound  is  heard  immediately  after  swallowing,  a  result  which 
has  been  explained  as  probably  due  to  insufficiency  of  the 
cardia.*  These  phenomena  led  Kronecker  and  Meltzer  to  modify 
their  previous  views.  They  now  maintained  that  the  swallowed 
mass  is  not  squirted  directly  into  the  stomach,  but  is  checked 
a  short  distance  above  the  cardia.  There  it  remains  until  over- 
taken by  the  succeeding  peristaltic  wave,  about  six  or  seven 
seconds  later,  when  it  is  pressed  onward  into  the  stomach. 

The  methods  employed  in  these  carefully-conducted  ex- 
periments were  possible  sources  of  error.  The  presence  of  one 
or  more  balloons  and  a  stomach -tube  in  the  oesophagus  may 
properly  be  regarded  as  disturbing  to  normal  deglutition.  What 
can  be  done  by  the  organism,  while  compensating  for  disturbing 
experimental  conditions,  may  not  be  the  normal  action  of  the 

*,  Hertz  has  suggested  (Brit.  M.  J.,  1908,  i.,  p.  132)  that  the  first  sound  is 
caused  by  the  impact  of  fluid  against  the  posterior  pharyngeal  wall,  for  it  is 
louder  in  the  prone  than  in  the  supine  position.  Since  it  can  invariably  be 
heard  in  the  neck  region,  it  seems  not  to  fit  the  occasional  character  which 
Meltzer  gave  it.  The  second  sound,  Hertz  states,  is  like  a  trickle  in  the 
upright  and  like  a  squirt  in  the  horizontal  posture.  It  corresponds  to  the  final 
disappearance  of  the  swallowed  mass  into  the  stomach. 


MASTICATION   AND   DEGLUTITION  15 

same  organism  in  a  more  natural  state.  Furthermore,  although 
Kronecker  and  Meltzer  themselves  declared  that  their  results 
were  true  for  liquids  and  semi- solids  only,  and  admitted  that  a 
dry  bolus  could  not  be  shot  down  the  gullet,  yet  the  use  of 
the  terms  "  liquid,"  "  swallowed  mass,"  and  "  bolus,"  easily, 
leads  to  the  inference  that  their  results  are  true  for  the  swallow- 
ing of  food  of  all  consistencies. 

With  the  purpose  of  studying  the  rate  of  movement  of  solids, 
semi-solids,  and  liquids,  in  the  normal  oesophagus,  Mr.  A.  Moser 
and  I  undertook,  in  the  autumn  of  1897,  observations  on  various 
animals  by  means  of  the  X  rays.  Thus  anaesthesia  could  be 
•dispensed  with,  no  operative  interference  would  be  required, 
only  the  food  itself  would  be  present  in  the  gullet ;  in  short,  the 
animal  could  swallow  its  food  under  quite  natural  conditions. 

Observations  were  made  on  the  long  neck  of  the  goose,  on  the 
cat,  dog,  horse,  and  man.  In  watching  the  process  of  swallowing 
in  the  goose,  the  neck  of  the  animal  was  extended  by  a  tall 
pasteboard  collar,  which  in  no  way  compressed  the  gullet.  A 
bolus  of  corn-meal  mush  placed  in  the  pharynx  was  seen  to 
descend  slowly  and  regularly.  About  twelve  seconds  elapsed 
while  the  bolus  was  moving  through  15  centimetres  of  the 
oesophagus.  Careful  records  indicated  a  slight  slowing  of  the 
movement  as  the  bolus  descended.  A  syrup  which,  when  mixed 
with  bismuth  subnitrate,  still  dropped  quickly  from  the  end  of 
a  glass  rod  was  used  as  a  liquid  mass.  This  liquid,  fed  through 
a  pipette,  also  passed  slowly  and  regularly  down  the  oesophagus, 
clearly  by  peristalsis.  The  rate  was  about  the  same  as  for  solid 
food.  In  the  bird,  therefore,  peristalsis  is  the  only  movement, 
without  regard  to  the  consistency  of  the  food.  The  quick 
propulsion  of  liquids  from  the  mouth  does  not  occur.  In  the 
absence  of  this  action  a  greater  reliance  on  gravity  is  observed. 
As  the  mouth  is  filled  the  head  is  raised,  and  the  fluid,  after 
trickling  into  the  oesophagus,  is  carried  onward  by  peristalsis. 
It  is  of  interest  to  note  that,  when  the  mylo-hyoid  muscles  are 
paralyzed  in  a  mammal,  the  animal  raises  the  head  in  swallowing,  _ 
after  the  manner  of  birds. 

In  observations  on  the  cat  and  dog,  gelatine  capsules  con- 
taining the  bismuth  powder  or  shreds  of  meat  wrapped  about  it 
were  used  as  more  or  less  "  solid  "  food.  For  soft  solids  a  mush 
of  bread  and  milk  was  selected,  so  fluid  as  to  be  easily  drawn  up 
into  a  large-bore  pipette,  and  yet  so  viscid  as  to  retain  the 


16  THE   MECHANICAL   FACTORS    OF   DIGESTION 

bismuth  powder  in  suspension  for  a  long  period.  After  trying 
a  number  of  other  methods,  we  finally  decided  that  a  simple 
mixture  of  milk  and  bismuth  subnitrate,  shaken  in  a  test-tube 
and  immediately  drawn  into  a  pipette,  was  the  most  satisfactory 
means  of  supplying  a  liquid  mass. 

Solid  food  passed  down  the  entire  oesophagus  of  the  cat  and  dog- 
by  peristalsis.  In  the  cat  the  rate  was  uniform  to  the  level  of 
the  heart ;  about  four  seconds  were  required  for  the  passage. 
In  the  lower  section,  from  the  heart  to  the  stomach,  the  rate  was- 
distinctly  slower.  The  distance  was  less  than  one- third  the 
entire  canal,  yet  the  time  spent  in  this  part  was  six  or  seven 
seconds,  or  three-fifths  of  the  entire  time  of  the  descent.  In  the 
dog  the  solid  bolus  was  quickly  discharged  into  the  oesophagus.,, 
and  descended  rapidly  for  a  few  centimetres,  sometimes  nearly 
to  the  base  of  the  neck.  Thereafter  the  rapidity  was  diminished  ;. 
yet  no  pause  was  observed — the  bolus  simply  moved  more  slowly. 
Unlike  the  cat  there  was  no  slackening  of  speed  below  the  level 
of  the  heart,  and  without  change  of  rate,  therefore,  the  mass  was 
passed  into  the  stomach.  Four  or  five  seconds  were  required  for 
the  descent  from  larynx  to  cardia. 

Semi-solids  were  carried  in  the  dog  and  cat  much  as  the  solids 
were  carried.  The  only  difference  observed  was  a  slightly  more 
rapid  passage  along  the  upper  oesophagus  in  the  cat.  Liquids 
were  forced  into  the  tube  at  a  more  rapid  rate  than  the  solids  and 
semi-solids.  In  the  cat  only  1-5  or  2  seconds  were  required  for 
the  liquid  to  pass  from  the  laryngeal  to  the  mid-heart  level.17 
Then,  after  a  pause  which  lasted  from  a  few  seconds  to  a  minute 
or  more,  the  oesophagus  apparently  contracted  above  the  liquid, 
and  pushed  it  slowly  into  the  stomach.  Sometimes  the  peristaltic 
wave  seemed  to  be  started  by  a  swallowing  movement,  though 
the  exact  course  of  the  contraction  could  not,  naturally,  be 
directly  observed.  In  the  dog,  liquids  were  evidently  squirted 
for  some  distance  along  the  cesophageal  tube.  To  free  the  tube 
from  any  disturbing  tension  or  compression,  the  head  of  the 
animal  was  released  from  the  holde:  and  held  in  the  hands. 
Sometimes  the  liquid  descended  rapidly  as  far  as  the  heart,  at 
other  tunes  no  farther  than  the  base  of  the  neck.  Without  a 
pause  it  then  passed  on  with  perfect  regularity  and  entered  the 
stomach.  Meltzer  has  reported  direct  observations  of  the  oesoph- 
agus of  the  anesthetized  dog,  and  states  that  swallowed 
liquids  are  projected  rapidly  a  varying  distance  along  the  tube, 


MASTICATION   AND   DEGLUTITION  17 

the  distance  depending  on  the  quantity  swallowed,  the  force  of  the 
swallowing  movement  and  the  degree  of  contraction  of  the 
lower  oesophagus.18  When  the  liquid  ceased  its  rapid  flight, 
instead  of  being  promptly  moved  onwards,  Meltzer  states  that 
it  suffered  a  considerable  delay  before  a  peristaltic  wave  arrived 
and  forced  it  along.  This  discrepancy  between  Meltzer's  and  our 
observations  was  probably  due  to  anaesthesia,  which  is  known  to 
interfere  greatly  with  oesophageal  peristalsis ;  for  Meltzer  has  since 
reported  that  objects  present  in  the  thoracic  oesophagus  of  the 
unanaesthetized  dog  are  at  once  carried  into  the  stomach  without 
the  aid  of  any  peristaltic  wave  started  by  the  act  of  swallowing.19 
This  peristalsis  of  local  origin,  which  Meltzer  has  denominated 
"  secondary  peristalsis,"  would  account  for  the  continuous  pro- 
gress of  a  swallowed  bolus  even  when  it  has  been  projected  deep 
into  the  oesophagus  by  the  forceful  movements  of  the  mouth. 

The  influence  of  consistency  of  food  was  further  demonstrated 
in  a  very  simple  way  by  our  observations  on  the  horse.  A  bolus 
made  from  masticated  hay  or  grain  can  be  seen  or  felt  passing 
along  the  horse's  oesophagus  at  the  rate  of  35  or  40  centimetres 
per  second.  Even  a  mixture  of  bran  and  water,  thin  enough  to 
run  easily  through  the  fingers,  was  not  carried  faster  than  the 
hay  or  grain.  But  liquids  were  shot  along  the  gullet  much  too 
rapidly  to  be  accounted  for  by  any  peristaltic  activity.  Anyone 
who  will  place  his  hand  under  the  lower  jaw  of  the  horse  while  the 
animal  is  drinking  will  find  in  the  energetic  contraction  of  the 
mylo-hyoids  a  sufficient  explanation  of  the  rapid  passage  of  water 
through  the  oesophagus.  The  rate  is  more  than  five  times  as 
rapid  as  that  of  solids  and  semi-solids. 

X-ray  observations  of  deglutition  in  the  human  being  revealed 
the  same  conditions  that  we  found  in  the  horse.  Gelatine 
capsules  were  seen  descending  steadily  and  regularly  at  a  rela- 
tively slow  rate  from  the  region  of  the  pharynx  to  a  point  below 
the  heart.  A  semi-solid  consisting  of  a  mush  of  bread  and  milk 
was  traced  over  the  same  course,  and  it  had  nearly  the  same  rate 
of  progression  as  the  solid.  In  both  cases  the  swallowed  material 
was  evidently  pushed  onward  by  peristalsis.  The  X-ray  observa- 
tions of  Lessen  on  persons  who  swallowed  potato  soup  confirm 
our  conclusion  that  the  passage  of  semi-solids  through  the 
oesophagus  is  not  sudden.20 

According  to  the  X-ray  studies  of  Hertz,  solids  pass  along  the 
human  oesophagus  slowly,  no  matter  what  the  position  of  the 

2 


18  THE   MECHANICAL   FACTORS    OF  DIGESTION 

body ;  the  time  required  when  the  solids  are  well  lubricated 
varies  between  eight  and  eighteen  seconds,  but  a  dry  bolus  may 
remain  above  the  cardia  many  minutes.21 

We  found  no  evidence  of  the  contraction  of  the  oesophagus  in 
three  sections,  as  Kronecker  and  Meltzer  reported.  If  the 
oesophagus  contracts  in  sections,  with  an  interval  of  two  or  three 
seconds  between  the  contraction  of  adjoining  sections,  we  should 
expect  a  checking  of  the  progress  of  the  swallowed  mass  at  each 
stage.  The  steady  progress  of  the  bolus,  as  we  observed  it, 
does  not  harmonize  with  the  view  that  successive  long  stretches 
of  the  oesophagus  undergo  each  a  single  contraction  simulta- 
neously throughout  its  length.  Schreiber,22  who  has  studied 
the  contractions  of  the  human  oesophagus  with  the  method  used 
by  Kronecker  and  Meltzer,  was  also  unable  to  find  a  separation 
of  the  tube  into  three  sections,  each  with  its  own  time  for  con- 
traction. Instead,  his  curves  revealed  the  existence  of  a  con- 
striction registered  gradually  later  as  the  recording  apparatus 
was  placed  gradually  deeper  in  the  oesophagus.  This  moving 
constriction  can  be  explained  only  as  a  peristaltic  wave.  As  in 
our  observations  on  the  cat,  Schreiber  found  in  man  that  peri- 
stalsis was  rapid  in  the  upper  oesophagus,  and  much  slower  in  the 
thoracic  portion. 

Although  Schreiber  showed  that  the  first  rise  in  Kronecker 
and  Meltzer's  records  could  be  obtained  when  the  oesophagus 
above  the  recording  balloon  was  closed,  or  when  the  swallow 
was  "  empty,"  the  possibility  of  rapid  passage  of  a  bolus  through 
the  oesophagus  was  not  thereby  excluded. 

Our  X-ray  observations  on  the  swallowing  of  liquids  in  the 
human  being  are  quite  in  accord  with  Kronecker  and  Meltzer's 
contention.  Water  holding  bismuth  subnitrate  in  suspension 
was  drunk  by  the  subject,  and  at  each  swallow  the  liquid  was 
projected  rapidly  through  the  pharynx  and  well  down  into  the 
thoracic  oesophagus  before  it  was  lost  to  view.  Hertz  was  able 
to  trace  the  passage  of  bismuth  salt  suspended  in  milk  all  the 
way  to  the  stomach  in  fourteen  normal  persons.  After  having 
been  "  shot  rapidly  down  the  greater  part  of  the  oesophagus,"  the 
fluid  was  forced  slowly  into  the  stomach.  Between  four  and 
eight  seconds  were  required  for  the  entire  process,  and  of  this 
time  about  half  was  spent  in  going  through  the  cardia.  In  the 
head-down  position  fluids  ascended  the  oesophagus  at  approxi- 
mately one-third  the  rate  of  descent  in  the  upright  position.23 


MASTICATION   AND    DEGLUTITION  19 

Mikulicz  became  convinced  by  repeated  cesophagoscopic  exam- 
inations that  not  only  is  the  resting  tube  in  the  thoracic  region 
wide  open  and  filled  with  air,  but  that,  owing  to  the  elasticity 
of  the  lungs,  the  pressure  prevailing  is  slightly  less  than  atmo- 
spheric.24 Doubtless  this  condition,  if  generally  present  in  man, 
is  highly  favourable  to  the  projectile  passage  of  liquids  from  the 
mouth  to  the  region  of  the  cardia. 

We  may  conclude  that  the  act  of  swallowing  varies  in  different 
animals  and  with  different  consistencies  of  food.  In  various 
mammals  studied  by  means  of  the  X  rays,  solid  and  soft  mushy 
foods  were  invariably  carried  down  by  peristalsis  ;  in  the  horse 
and  man,  liquids  were  forcibly  discharged  along  the  oesophagus 
by  the  quick  contraction  of  muscles  of  the  mouth,  and  even  in 
the  dog  and  cat  liquids  descended  for  some  distance  faster  than 
more  viscid  masses.  Whether  liquids  invariably  descend  to  the 
stomach  at  a  rapid  rate  doubtless  depends,  as  Meltzer  has  sug- 
gested, on  the  amount  swallowed,  the  force  of  the  swallowing 
movement,  and  the  degree  of  contraction  of  the  gullet.  Since 
two  of  these  three  factors  are  under  voluntary  control,  it  is  quite 
possible  that  mammals  needing  for  any  reason  to  propel  liquids 
rapidly  through  the  oesophagus  would  in  that  necessity  be  able 
to  do  so. 

REFERENCES. 

1  See  Fermi,  Arch.  f.  Physiol.,  1901,  Suppl.,  p.  98. 

2  Lehmann,  Sitzunjsb.  d.  Phys.-Med.  Ges.  zu.  Wurzburj,  1900,  p.  41. 

3  Gaudenz,  Arch.  f.  Hyg.,  1901,  xxxix.,  p.  231. 

4  Gaudenz,  loc.  cit.,  pp.  238,  242. 

5  Black,  Dent.  Cosmos,  1895,  xxxvii.,  p.  474. 

6  Head,  Dent.  Cosmos,  1906,  xlviii.,  p.  1191. 

7  Pawlow,  The  Work  of  the  Digestive  Glands,  London,  1902,  p.  50. 

8  Hornborg,  Skand.  Arch.  f.  PhysioL,  1904,  xv.,  p.  248. 

9  Magendie,  Prlcis  JKllmentaire  de  Physiologie,  Paris,  1817,  ii.,  p.  58. 

10  Falk  and  Kronecker,  Arch.  f.  PhysioL,  1880,  p.  296. 

11  Einthoven,  Hdb.  d.  Laryngol.  u.  Rhind.,  Vienna,  1899,  ii.,  p.  53. 

12  See  the  radiographic  study  by  Eykmann,  Arch.  f.  d.  ges.  Physiol.,  1903, 
xcix.,  p.  521. 

13  Kronecker  and  Meltzer,  Arch.  /.  Physiol.,  1880,  p.  446. 

14  Meltzer,  Proc.  Soc.  Exper.  Bid.  M.,  New  York,  1907,  iv.,  p.  41. 

15  Kronecker  and  Meltzer,  Arch.  f.  Physiol.,  1883,  Suppl.,  p.  341  ;  Meltzer, 
N.  York  M.  J.,  1894,  lix.,  p.  389. 

16  Meltzer,  Centralbl.  f.  d.  Med.  Wissensch.,  1883,  p.  1. 

17  Cannon  and  Moser,  Am.  J.  Physiol.,  1898,  L,  p.  440. 

18  Meltzer,  J.  Exper.  M.,  1897,  ii.,  p.  463. 

19  Meltzer,  Proc.  Soc.  Exper.  Bid.  M.,  New  York,  1907,  iv.,  p.  36.     Also  for 
rabbit,  see  Zentralbl.  f.  Physiol.,  1906,  xix.,  p.  993. 

20  Lossen,  Mitth.  a.  d.  Grenzgeb.  d.  M.  u.  Chir.,  1903,  xii.,  p.  363. 

21  Hertz,  Brit.  M.  J.,  1908,  L,  p.  131. 

22  Schreiber,  Arch.  f.  exper.  Path.  u.  Pharmakol.,  1901,  xlvi.,  p.  442. 

23  Hertz,  loc.  cit.,  p.  131. 

4  Mikulicz,  Mitth.  a.  d.  Grenzgeb.  d.  M.  u.  Chir.,  1903,  xii.,  p.  596. 


CHAPTER  III 
THE  NERVOUS  CONTROL  OF  DEGLUTITION 

As  the  word  implies,  the  oesophageal  tube  is  merely  a  "  food- 
carrier,"  serving  to  transmit  nutriment  quickly  from  the  first 
digestive  region  to  the  second.  The  variations  in  the  rate  of 
transmission  in  different  animals  and  in  different  parts  of  the 
oesophagus  of  the  same  animal  can  be  explained  by  differences 
in  histological  structure.  Thus  the  uniform  slow  peristalsis  of 
the  goose  is  performed  by  an  oesophagus  composed  entirely  of 
smooth  muscle.  The  change  from  rapid  to  slow  peristalsis  near 
the  heart  region  in  the  cat's  oesophagus  corresponds  to  a  change 
from  striated  to  smooth  muscle  in  the  structure  of  the  wall. 
The  absence  of  any  similar  slackening  of  speed  in  the  lower 
thoracic  region  of  the  dog  is  accounted  for  by  the  absence  of  the 
change  of  structure — the  dog's  oesophagus  is  composed  of  striated 
muscle  throughout.  The  more  rapid  contraction  of  striated 
muscle  compared  with  smooth  muscle  gives  a  reason  for  the 
bolus  reaching  the  dog's  stomach  in  four  or  five  seconds,  instead 
of  requiring  nine  seconds  or  more  as  in  the  shorter  oesophagus 
of  the  cat.  The  slow  contraction  of  the  lower  portion  of  the  human 
oesophagus,  noted  by  Kronecker  and  Meltzer,  and  by  Schreiber, 
is  explained  by  the  fact  that  this  portion  is  composed,  like  the 
oesophagus  of  the  cat,  of  smooth  muscle.1  These  distinctions  are 
important  for  our  understanding  of  the  action  of  the  oesophagus 
in  relation  to  its  inner vation. 

The  process  of  swallowing  transfers  the  food  from  the  short 
region  in  which  it  is  subject  to  voluntary  control  to  that  exten- 
sive region  in  which  the  digestive  processes  are  automatically 
managed  without  affecting  consciousness  or  being  disturbed  by 
whims  of  the  will.  Not  until  the  waste  from  the  swallowed  food 
appears  at  the  terminus  of  the  canal  does  direct  voluntary 
interference  again  become  possible.  Indeed,  the  region  at  the 

20 


THE  NERVOUS  CONTROL  OF  DEGLUTITION     21 

start  where  we  can  do  as  we  wish  with  the  food  is  only  that 
concerned  with  mastication  ;  as  soon  as  swallowing  begins,  the 
bolus  slips  suddenly  into  the  grip  of  a  train  of  reflexes  from  which 
there  is  normally  no  recall.  Like  other  reflex  mechanisms,  the 
arrangements  for  swallowing  involve  afferent  paths  and  efferent 
paths.  The  remarkable  provisions  for  efficient  action,  especially 
in  the  oesophageal  region,  make  the  innervation  of  deglutition 
peculiarly  interesting. 

The  origins  of  the  afferent  impulses,  which  start  the  series 
of  reflexes,  have  been  studied  in  different  animals  ;  :and  variations 
have  been  found  in  their  locations,  just  as  variations  were  found 
in  the  rate  of  passage  along  the  oesophagus.  The  areas  at  which 
the  impulses  can  be  started  have  been  classified  into  the  most 
sensitive  area  or  "  chief  spot "  for  initiating  the  swallowing 
reflex,  and  accessory  spots,  of  less  sensitiveness,  from  which  the 
reflex  is  not  so  readily  aroused.  According  to  the  careful  in- 
vestigations of  Kahn,2  the  chief  spot  in  each  animal  is  found  in 
the  natural  path  from  mouth  to  oesophagus  ;  the  accessory  spots 
lie  in  out-of-the-way  places,  into  which,  however,  small  particles 
of  food  may  be  driven.  Thus  in  the  dog  and  cat  the  chief  spot 
is  an  area  on  the  back  wall  of  the  pharynx,  opposite  the  posterior 
opening  of  the  mouth  cavity — an  area  supplied  by  the  glosso- 
pharyngeus  nerve.  Accessory  spots  are  present  on  the  upper 
surface  of  the  soft  palate,  supplied  by  the  glosso-pharyngeus  and 
the  second  branch  of  the  trigeminus,  and  on  the  dorsal  face  and 
base  of  the  epiglottis,  supplied  by  the  superior  laryngeal  nerve. 
In  monkeys  the  chief  spot  is  in  the  tonsillar  region,  and  accessory 
spots  appear  at  the  entrance  to  the  larynx,  on  the  back  and 
base  of  the  epiglottis,  and  on  the  wall  of  the  pharynx. 

These  spots  were  found  by  touching  the  mucous  membrane  of 
the  mouth  and  pharynx  here  and  there  until  the  reflex  occurred. 
The  chief  spots  are  extraordinarily  sensitive  to  mechanical 
stimulation,  and  the  reflexes  which  they  call  into  activity  are 
unusually  indefatigable.  Wassilieff,  for  example,  was  able  by 
touching  one  point  in  the  mucous  membrane  to  evoke  in  succes- 
sion fifty  acts  of  deglutition.3 

Accurate  observations  on  man  as  to  the  most  sensitive  areas 
for  inducing  the  deglutition  reflex  have  not  been  made,  though  in 
all  probability  the  back  wall  of  the  pharynx  and  areas  near  the 
base  of  the  tongue,  when  touched  by  foreign  bodies,  will  evoke 
the  movements.  The  perfect  reflex  character  of  deglutition,  and 


THE   MECHANICAL   FACTORS    OF   DIGESTION 

its  absolute  dependence  on  incoming  impulses  from  special  spots 
in  the  mouth  and  pharynx,  was  clearly  demonstrated  by  Wassilieff. 
He  swallowed  a  small  sponge  moistened  with  cocaine,  and  imme- 
diately drew  the  sponge  back  by  means  of  a  thread  attached  to 
it.  The  ability  to  swallow  was  for  some  minutes  entirely  lost, 
and  the  saliva,  which  was  abundantly  secreted,  had  to  be  ex- 
pectorated. Just  as  there  must  be  a  sensitive  region  to  be 
stimulated,  so  likewise  there  must  be  an  object  to  stimulate  it. 
We  need  only  to  swallow  several  times  in  rapid  succession,  until 
no  more  saliva  is  present  in  the  mouth,  to  observe  how  impossible 
the  act  becomes  in  the  absence  of  a  peripheral  stimulus.  Under 
normal  conditions  of  ingesting  food,  the  sensitive  spot  can  be 
stimulated  either  by  liquid  buccal  contents  flowing  back  upon  it, 
when  involuntary  swallowing  occurs,  or  by  more  or  less  solid 
food-masses  being  voluntarily  pushed  over  the  base  of  the  tongue 
and  into  the  pharynx. 

The  region  of  the  central  nervous  system  to  which  the  afferent 
impulses  travel  is,  according  to  Marckwald,4  situated  in  the  floor 
of  the  fourth  ventricle,  above  the  centre  of  respiration.  From 
this  centre  of  deglutition  in  the  medulla  pass  out  the  motor 
impulses,  which,  distributed  by  a  variety  of  nerves,  produce  the 
remarkably  rapid  and  orderly  sequence  of  movements  that  give 
the  bolus  its  initial  push  and  continue  it  on  its  course.  By  the 
hypoglossus  nerve  impulses  pass  to  the  tongue,  by  the  third 
branch  of  the  trigeminus  to  the  mylo-hyoid,  by  the  glosso- 
pharyngeus  and  the  pharyngeal  branch  of  the  vagi  to  the  muscles 
of  the  pharynx,  and  by  several  vagus  branches  to  the  entire 
length  of  the  oesophagus.  We  can  readily  understand  into  what 
a  chaos  all  this  wonderfully  co-ordinated  mechanism  is  thrown 
by  the  incidence  of  bulbar  disease. 

We  shall  now  turn  our  attention  to  the  important  part  played 
by  the  vagi  in  the  nervous  control  of  the  cesophagus.  According 
to  Kahn,5  the  innervation  of  the  thoracic  portion  of  the 
cesophagus  is  the  same  in  the  cat,  dog,  and  monkey — merely 
the  cesophageal  branches  of  the  vagi  which  enter  the  wall  of  the 
tube  just  above  the  hilus  of  the  lungs.  Still  other  branches, 
however,  enter  the  wall  near  the  diaphragm.  To  the  neck 
region,  in  all  three  animals,  the  recurrent  laryngeus  supplies 
motor  fibres — in  the  dog  and  cat  only  to  the  lower  portion,  but 
in  the  monkey  to  the  whole  extent  of  the  cervical  oesophagus. 
Other  branches  of  the  vagi,  as  well  as  fibres  from  the  cervical 


THE  NERVOUS  CONTROL  OF  DEGLUTITION     23 

sympathetic,  are  distributed  directly  to  the  upper  portion  of  the 
tube  in  the  neck  region.  Stimulation  of  the  sympathetic  fibres 
produces  no  obvious  effect.  Stimulation  of  the  vagus  nerve  on 
either  side  causes  strong  simultaneous  contraction  of  the  entire 
oasophagus.  Clearly  the  vagi  are  the  motor  nerves  of  the  gullet. 
There  are  several  ways,  however,  in  which  they  cause  an  order!}7 
peristaltic  wave  to  progress  along  the  tube. 

In  1846,  Wild  reported  experiments  which  showed  that  if  the 
O3sophagus  is  divided,  or  merely  has  a  thread  tied  tightly  about 
it,  the  peristaltic  wave  is  definitely  blocked  at  the  point  of  inter- 
ference. From  this  observation  he  drew  the  conclusion  that 
oesophageal  peristalsis  is  due  to  a  series  of  reflexes  starting  in 
the  mucous  membrane  of  the  oesophagus  itself — a  series  at  once 
stopped  by  any  interruption  of  the  continuity  of  the  tube.6 
This  conclusion  was  accepted  without  qualification  until  1876, 
when  Mosso  published  experiments  which  indicated  the  possi- 
bility of  central  origin  of  the  peristaltic  wave.  He  used  the 
methods  of  Wild,  but  placed  a  small  wooden  ball  in  the  oesophagus 
below  the  point  where  the  tube  had  been  transected.  When  a 
wave,  started  by  a  swallowing  movement,  had  traversed  the 
upper  section,  it  did  not  stop  at  the  point  of  incision,  but  in  due 
time  reappeared  below,  and  carried  the  ball  to  the  stomach. 
Continuation  of  the  wave  across  an  open  space  led  Mosso  to  a 
conclusion  opposite  that  of  Wild — viz.,  that  oesophageal  peri- 
stalsis is  originated  step  by  step  in  the  central  nervous  system. 

The  discrepancy  between  Wild's  and  Mosso's  observations 
and  inferences  had  no  explanation  until  Meltzer,  in  1899,  repeated 
the  experiments,  and  was  able  by  varying  the  conditions  to  obtain 
one  result  or  the  other,  as  he  pleased.  The  key  to  the  situation 
lay  in  recognizing  the  effect  of  anaesthesia.  In  very  deep  anaes- 
thesia water  can  be  introduced  into  the  mouth,  and  no  deglutition 
will  follow.  When  anaesthesia  is  slightly  less  deep,  reflex  contrac- 
tions of  buccal  and  pharnygeal  muscles  occur,  but  they  are  not 
followed  by  oesophageal  peristalsis.  With  still  less  deep  anaes- 
thesia a  peristaltic  wave  follows  a  swallow  if  material  is  pressed 
into  the  gullet  from  the  mouth,  but  fails  if  the  swallow  is  empty. 
It  therefore  fails  also  beyond  a  compressed  or  incised  region. 
With  very  light  anaesthesia  the  entire  process  occurs  quite 
normally,  and  the  wave  will  pass  an  interruption  in  the  con- 
tinuity of  the  tube.  According  to  Meltzer's  results,  Wild  ob- 
served conditions  which  appear  in  deep  anaesthesia,  and  discovered 


THE   MECHANICAL   FACTORS    OF   DIGESTION 

the  reflex  peristalsis  which  can  originate  in  the  oesophagus  itself. 
Mosso,  on  the  other  hand,  who  studied  the  conditions  in  light 
anaesthesia,  discovered  the  central  origin  of  the  procession  of 
ossophageal  peristalsis,  which  normally  prevails.7 

Two  mechanisms  are  therefore  present  to  control  the  course 
of  a  bolus  along  the  gullet.  One  mechanism  requires  only  a 
single  afferent  impulse  to  start  it,  the  impulse  arising  usually 
at  the  chief  or  most  sensitive  spot  in  the  mouth  or  pharynx. 
This  ingoing  impulse  spreads  in  the  centre  for  deglutition,  and 
in  proper  order  evokes  the  series  of  nervous  discharges  which 
precipitate  the  rapid  sequence  of  contractions  in  the  mouth  and 
throat,  and  move  the  annular  constrictions  along  the  oesophagus, 
which  constitute  normal  deglutition.  The  continuity  of  the 
gullet  is  not  necessary  for  the  progress  of  this  form  of  peristalsis, 
but  its  nervous  control  is  especially  sensitive  to  anaesthetics. 
Meltzer  suggests  calling  this  the  higher  reflex  mechanism,  which 
gives  rise  to  "  primary  peristalsis."  The  other  mechanism 
consists  of  a  succession  of  reflexes,  each  provided  with  an  afferent 
path  which  leads  to  a  motor  discharge  to  the  region  immediately 
above.  Thus  the  bolus  by  its  very  presence  would  cause  a  con- 
traction which  would  press  it  downwards  to  the  stomach.  This 
accessory  mechanism  is  dependent  on  the  integrity  of  the 
oesophageal  tube,  and,  although  requiring  the  presence  of  both 
vagus  nerves,  is  more  resistant  than  the  higher  mechanism  to 
anaesthetics.  It  has  been  called  the  lower  reflex  mechanism, 
and  its  activity  "  secondary  peristalsis."8 

The  observations  of  Kronecker  and  Meltzer  on  the  innerva- 
tion  of  deglutition  were  concerned  with  influences  affecting  the 
process  through  its  central  control.  When  a  series  of  swallowing 
movements  were  made,  as  in  drinking  a  glass  of  water,  they 
found  that  the  peristaltic  wave  appeared  only  after  the  last 
swallow.  Thus  each  act  of  deglutition  can  not  only  rouse  its 
own  oesophageal  contraction,  but  can  at  the  same  time  inhibit 
the  appearance  of  an  oesophageal  contraction  in  process  of  being 
roused  by  a  previous  swallow.  On  the  other  hand,  if  a  peristaltic 
wave  has  just  been  started  when  another  swallow  is  taken,  this 
first  wave  is  not  stopped  by  the  second  swallow,  nor  is  there  a 
superposition  of  a  second  wave  on  the  first.  The  second  motor 
discharge  is  only  sent  out  after  the  contraction  following  the 
first  discharge  has  been  completed.  There  is,  then,  here  a  clear 
refractory  phase  which  prevents  continuous  contraction  of  the 


THE  NERVOUS  CONTROL  OF  DEGLUTITION     25 

cesophageal  muscles.  The  inhibitory  mechanism  Kronecker  and 
Meltzer  were  able  to  bring  into  action  by  exciting  the  glosso- 
pharyngeal  nerve  ;  whereupon  the  strongest  stimuli  to  degluti- 
tion were  without  effect.  That  the  glosso-pharyngeus  exercises 
a  tonic  inhibitory  influence*  is  indicated  by  the  effect  of  cutting 
it :  the  oesophagus  enters  a  tonic  contraction  which  may  persist 
for  more  than  a  day.9 

Although  oesophageal  peristalsis  resembles  in  appearance 
gastric  and  intestinal  peristalsis,  nevertheless  the  waves  passing 
along  the  gullet,  unlike  those  of  the  rest  of  the  alimentary  canal, 
have  come  to  be  regarded  as  due  exclusively  to  impulses  arriving 
by  way  of  the  vagi.  Thus,  Meltzer10  states  :  "  It  is  now  generally 
assumed  that  the  orderly  progress  of  the  peristalsis  in  the  oesoph- 
agus is  exclusively  of  central  origin."  More  recently  Starling11 
has  declared  :  "  The  orderly  progression  of  the  peristaltic  wave 
along  the  walls  of  the  tube  (oesophagus)  is  dependent  on  the 
integrity  of  the  branches  of  the  vagus  nerve,  by  which  the 
medullary  centre  is  united  to  the  gullet.  Division  of  these  nerves 
destroys  the  power  of  swallowing." 

The  evidence  that  oesophageal  peristalsis  is  managed  through 
the  vagi  is  found,  as  we  have  seen,  in  the  anatomical  distribution 
of  the  nerves  to  the  tube,  and,  as  just  indicated,  in  the  effect 
of  cutting  these  nerves.  Thus  secondary  peristalsis  was  entirely 
abolished,  Meltzer  observed,  as  soon  as  the  vagi  were  severed  ; 
and  the  material  introduced  was  no  longer  moved  downward.12 
This  stasis  of  food  in  the  oesophagus  after  vagus  section  was, 
indeed,  recorded  by  Keid  as  long  ago  as  1839.13  Keid's  observa- 
tions were  quoted  by  Volkmann,14  and  Volkmann's  article  has 
been  repeatedly  referred  to  by  recent  writers  as  authority  for 
the  failure  of  deglutition  after  severance  of  the  vagi. 

In  enunciating  the  doctrine  that  extrinsic  innervation  of  the 
cesophagus  is  the  necessary  condition  for  activity,  two  important 
considerations  seem  to  have  been  overlooked — first,  the  difference 
between  the  immediate  effects  of  vagus  section  and  the  later 
possible  recovery  of  a  normal  state  ;  and,  second,  the  muscular 
structure  of  the  lower  fourth  or  fifth  of  the  tube,  which,  as  we 
have  noted,  is  composed  in  many  animals  largely  or  entirely 

*  The  reader  will  recall  that  the  glosso-pharyngeus  has  been  reported  as  the 
afferent  nerve  for  the  initiation  of  swallowing.  Possibly  the  observation  of 
Kitajew  (Jahresb.  il.  d.  Fartschr.  d.  PhysioL,  1908,  p.  151),  that  weak  stimulation 
of  this  nerve  inhibits  deglutition,  while  strong  stimulation  causes  frequent  and 
strong  contractions  of  the  oesophagus,  gives  a  clue  to  the  discrepancy. 


26  THE   MECHANICAL   FACTORS    OF   DIGESTION 

of  smooth  fibres,  well  supplied  with  a  myenteric  plexus,  and 
resembling  in  all  essentials  the  muscular  wall  of  the  stomach 
and  intestine.  In  1906  I  had  occasion  to  observe  that  there 
may  be  for  some  time  after  vagus  section  a  total  absence  or 
notable  inefficiency  of  gastric  peristalsis,  with  a  subsequent 
remarkable  restoration  of  function.  The  local  mechanisms, 
at  first  inert  after  removal  of  vagus  influence,  later  prove  able 
to  continue  gastric  peristalsis  in  an  almost  normal  manner.15 
If  it  is  possible  for  the  stomach  thus  to  recover  from  a  primary 
paralysis,  may  not  the  oesophagus,  at  least  that  part  of  it  similar 
in  all  essential  respects  to  the  stomach  structure,  be  able  to- 
recover  likewise  from  a  primary  paralysis  ? 

An  answer  to  the  question  was  found  by  severing  in  the  cat. 
the  lower  fourth  of  whose  oesophagus  is  supplied  with  smooth 
muscle,  the  two  vagus  nerves* — the  right  below  the  origin  of 
the  recurrent  laryngeal,  the  left  in  the  neck — and  subsequently 
studying  by  means  of  the  X  rays  the  movements  of  the  food  in 
the  oesophagus.  An  account  of  a  typical  case  will  present  the 
results. 

Two  days  after  section  of  the  right  vagus  nerve,  the  left  was 
cut,  but  just  before  the  second  operation  meat  wrapped  about 
some  bismuth  subnitrate  was  seen  moving  regularly  along  the 
oesophagus  and  into  the  stomach.  The  next  day  finely  ground 
meat  was  fed  ;  it  was  carried  normally  through  the  cervical 
portion  of  the  tube,  but  promptly  stopped  at  the  top  of  the 
thorax.  As  bolus  after  bolus  was  swallowed,  the  thoracic 
oesophagus  became  filled  with  a  distending  mass.  Continuous 
observation  for  forty-five  minutes  revealed  no  sign  of  activity 
in  the  gullet,  and  no  food  entered  the  stomach. 

On  the  day  following — the  second  day  after  severance  of  the 
left  vagus  nerve — nothing  of  the  accumulated  mass  was  found 
in  the  oesophagus.  Now  a  spoonful  of  mush  mixed  with  sub- 
nitrate  of  bismuth  was  given.  It  was  quickly  passed  to  the 
top  of  the  thorax,  and  in  four  minutes  it  was  spread,  apparently 
by  rhythmic  changes  of  pressure  due  to  respiration,  as  a  long, 
slender  mass  even  to  the  diaphragm.  During  another  four 
minutes  the  mass  lay  without  being  further  affected.  Then  a 
second  spoonful  of  the  mush  was  given.  When  this  new  material 
was  pressed  into  the  thoracic  oesophagus,  the  lumen  was  enlarged 
to  almost  twice  its  former  diameter.  Immediately  a  con- 
striction of  the  cesophageal  wall  occurred  at  the  level  of  the  lower 
half  of  the  heart.  This  constriction  moved  toward  the  stomach, 

*  In  all  operations  the  animals  were,  of  course,  under  complete  general 
anaesthesia. 


THE   NERVOUS    CONTROL   OF   DEGLUTITION  27 

and  was  followed  by  others  that  also  moved  downward. 
The  first  waves  failed  to  drive  food  through  the  cardia  ;  the 
food  slipped  back  through  the  moving  ring.  Later  waves,  how- 
ever, were  more  effective,  and  pushed  food  into  the  stomach. 
The  remnant  of  the  mush  in  the  gullet  was  now  extended  again 
in  a  slender  strand.  During  ten  minutes  more  of  continuous 
observation,  no  further  change  was  seen.  The  next  morning 
there  was  no  food  in  the  cage  and  none  in  the  oesophagus.  The 
waste  was  in  the  large  intestine. 

On  the  third  day  the  animal  took  three  spoonfuls  of  the  food, 
which  filled  the  thoracic  oesophagus  to  stretching.  Imme- 
diately, at  the  level  of  the  lower  half  of  the  heart,  a  constriction 
appeared  that  passed  downward,  causing  as  it  moved  a  marked 
bulging  of  the  tube  in  front.  Some  of  the  food  surely  escaped 
backward  through  the  advancing  ring.  This  wave  was  immedi- 
ately followed  by  a  second,  starting  from  the  heart  level,  and 
pushing  downward  in  a  manner  similar  to  the  first.  The  second 
wave  forced  food  into  the  stomach.  The  remnant  became 
extended  to  the  diaphragm  ;  but  only  after  four  minutes  did 
another  ring  start  at  the  heart  level,  and  push  the  lower  end  of 
the  column  into  the  stomach.  Again  the  remnant  was  extended 
to  the  diaphragm.  Except  occasional  deep  stationary  con- 
strictions, at  the  heart  level,  there  was  no  change  for  eight 
minutes.  Then  a  ring  formed  just  above  the  diaphragm,  and 
pushed  food  into  the  stomach ;  and  another  ring,  immediately 
above,  cut  off  the  lower  end  of  the  remaining  mass,  and  likewise 
forced  this  bit  of  food  through  the  cardia.  The  rest  of  the 
cesophageal  accumulation  was  now  but  a  slight  strand  in  the 
upper  thoracic  region.  For  thirty- eight  minutes  of  observation 
it  remained  unmoved  in  that  situation. 

On  the  seventh  day  the  thoracic  oesophagus  was  filled,  through 
a  rubber  tube,  with  thin  starch  paste  (3  grammes  to  100  c.c. 
water)  mixed  with  bismuth  subnitrate.  At  once  after  the  in- 
jection, one  constriction  after  another  formed  in  rapid  succession, 
each  cutting  off  the  extremity  of  the  repeatedly  extended  mass 
and  moving  it  through  the  cardia.  As  judged  by  gently  feeling 
the  larynx,  there  was  no  swallowing  in  this  process  ;  the  action 
was  a  local  response  to  the  presence  of  material  in  the  lower 
gullet.  Thus,  by  repeated  reductions  from  below,  the  column 
of  food  was  gradually  carried  away  until  only  a  slender  remnant 
was  left.  This  was  slowly  moved  below  the  heart,  but  there  it 
stayed  for  half  an  hour.  "  At  the  end  of  that  period  a  small  bit 
of  meat,  with  bismuth  subnitrate  adherent,  was  fed.  The  meat 
moved  smoothly  through  the  cervical  region,  but  stopped  at 
the  top  of  the  thorax.  Now  the  slender  mass  below  was 
gathered  together  and  swept  into  the  stomach.  Sixteen 
minutes  were  required  for  the  meat  to  come  to  the  level  of 


THE   MECHANICAL    FACTORS    OF   DIGESTION 

the  lower  half  of  the  heart.  Again  nothing  interpretable  as  a 
constriction  was  seen  in  the  thoracic  oesophagus  above  the 
heart.  Below  the  heart,  however,  the  meat,  which  had  been 
separated  into  two  pieces,  was  carried  by  peristalsis  into  the 
stomach. 

Twenty-three  days  later  the  animal  was  again  given  starch 
paste  as  before,  with  the  same  results.  While  there  was  still 
a  considerable  amount  of  the  paste  above  the  heart  level,  swallow- 
ing movements  were  caused  by  tickling  the  larynx.  Most 
careful  scrutiny  showed  no  sign  of  the  passage  of  a  wave  over 
the  food  in  the  upper  thoracic  region. 

In  the  foregoing  record  of  the  gradual  recovery  of  function  in 
the  lower  oesophagus,  several  points  stand  out  significantly  : 

1.  Immediately   after  operation,  and  for  twenty-four   hours 
at  least  thereafter,  it  is  easy  to  gather  evidence  of  complete 
paralysis  of  the  oesophagus.     In  one  instance  during  this  first 
period  food  was  observed  stagnating  in  the  gullet  for  five  hours, 
and  in  another  instance  for  seven  hours,  after  feeding.     But 
evidently  in  the  cat  a  distinction  must  be  made  between  this 
primary    paralysis    of    the    whole    oesophagus    after    bilateral 
vagotomy,    and   a   secondary  recovery  of   certainly  the  lower 
half  of  the  thoracic  portion. 

2.  After  a  return  of  peristaltic  activity  in  the  lower  oesophagus, 
an  important  factor  for  arousing  that  activity  seems  to  be  the 
stretching  of  the  oasophageal  wall.     A  slender  mass  spread  along 
the  tube  may  lie  for  some  time  unmoved  ;  the  addition  of  a 
second  mass,  which  causes  a  stretching  of  the  wall,  results  in 
the  instant  appearance  of  circular  constrictions  and  peristaltic 
movements.     And,  similarly,   after  repeated    reductions    have 
rendered  the  strand  of  food  more  attenuated,  it  lies  for  longer 
periods  unaffected  by  oesophageal  contractions.     The  reaction 
of  the  oesophageal  wall  to  the  presence  of  a  stretching  mass  is 
a  local  reaction,  occurring  without  centrally  initiated  movements 
of  deglutition.     In  this  respect  it  is  similar  to  movements  of 
the  alimentary  canal  below  the  cardia.     The  lower  oesophagus 
seems  to  become  more  responsive  to  the  presence  of  contained 
material  as  time  elapses,  for  the  material  is  driven  into  the 
stomach  with  increasing  rapidity,  and  even  slender  masses  are 
sufficient   cause   for   peristalsis.     Apparently   the   recovery   of 
activity  is  due  to  a  restoration,  in  some  manner,  of  the  capacity 
for  exhibiting  tension  when   stretched — a   capacity  ordinarily 
maintained  by  vagus  influences,  but  intrinsically  developed  when 


THE   NERVOUS    CONTROL   OF   DEGLUTITION  29 

those   influences   are   lost.     This,   however,   is   a   fundamental 
matter  which  we  must  deal  with  later. 

3.  A  difficulty  in  forcing  food  through  the  cardia  explains 
to  some  extent  the  slower  emptying  of  the  gullet  during  the 
first  days  after  operation.     That  the  cardia  of  the  cat  offers 
an  obstacle  to  easy  passage  into  the  stomach  after  bilateral 
vagotomy,  is  proved  by  the  fact  that  strong  peristaltic  waves, 
so  strong  as  to  produce  a  very  marked  bulging  of  the  tube  in 
front  of  them  as  they  advance,  have  failed  to  force  food  into 
the  stomach.     Indeed,  three  days  after  cutting  the  second  vagus 
nerve  I  have  seen  almost  exactly  the  same  repetition  of  deep 
constrictions  and  vigorous  peristaltic  movements  in  the  lower 
oesophagus  as  occur  in  the  small  intestine  in  case  of  obstruction.16 
The  opposition  at  the  cardia  was  also  noted  when  in  these 
animals  attempts  were  made  to  pass  a  tube  into  the  stomach. 

4.  Throughout   these   observations   a   marked   contrast   was 
noted  between  the  activity  of  the  lower  half  of  the  thoracic 
oesophagus   and  the  persistent   inactivity   of  the   upper  half. 
Absence  of    peristalsis  from  the  region   above  the  heart  was 
as  true  a  month  after  the  second    vagus  was  severed  as   it 
was  during  the  first  twenty-four  hours.     Is  there  any  difference 
of  condition  between  these  two  parts  of  the  thoracic  oesophagus 
which  might  account  for  their  difference  of  action  after  vagus 
section  ?     Leaving  one  recurrent  laryngeal  nerve,  as  we  know, 
still  provides  innervation  for  the  cervical  oesophagus  ;  but  cutting 
off  all  vagus  supply,  except  one  recurrent  laryngeal,  destroys 
the  extrinsic  innervation  of  the  gullet  between  the  base  of  the 
neck  and  the  cardia.     In  this  thoracic  region  the  oesophagus  is 
provided  with  two  kinds   of  muscular  fibres.      A  histological 
examination  of  the  oesophagus  of  the  animal  on  which  were 
made  the  detailed  observations  reported  above   showed  that 
the  musculature  of  the  upper  half  of  the  thoracic  region  was 
composed  predominantly  of  striped  fibres,  whereas  the  muscula- 
ture of  the  lower  half,  over  which  peristalsis  continued  after 
vagus  section,  was  composed  almost  wholly  of  unstriped  fibres. 
Since  the  difference  between  the  cervical  oesophagus,  which  acted 
normally,  and  the  upper  thoracic  oesophagus,  which  failed  to  act, 
was  that  the  former  had  in  all  cases  a  recurrent  laryngeal  supply, 
while  the  latter  had  no  outside  nerve  connection,  the  conclusion 
is  justified  that  that  part  of  the  tube  which  is  composed  of  striped 
muscles  fibres  is  paralyzed  when  vagus  impulses  are  removed  from 


30  THE   MECHANICAL   FACTORS    OF   DIGESTION 

it.  The  general  conclusion,  however,  that  the  entire  oesophagus 
is  put  out  of  action  by  severance  of  the  vagi  must  be  modified. 
That  part  of  the  tube  which  is  composed  of  unstriped  muscle  is, 
like  other  similar  parts  of  the  alimentary  canal,  capable  of  quite 
perfect  peristaltic  activity  without  the  aid  of  extrinsic  nerves. 

The  validity  of  these  conclusions  was  confirmed  by  observa- 
tions on  the  rabbit  and  the  monkey  (rhesus).  In  the  rabbit  no 
cesophageal  peristalsis  was  seen  at  any  time  after  severance  of 
the  second  vagus  nerve,  although  one  animal  was  kept  alive  and 
examined  from  time  to  time  for  two  weeks  after  the  operation. 
In  the  monkey,  on  the  other  hand,  the  results  were  similar  to 
those  in  the  cat.  Three  hours  after  the  second  vagus  was  sec- 
tioned, mashed  banana  mixed  with  subnitrate  of  bismuth, 
swallowed  by  the  monkey,  was  at  once  carried  to  the  upper 
thoracic  oesophagus,  where  it  rested.  More  banana  forced  some 
of  the  mass  in  the  gullet  to  the  level  of  the  heart.  As  soon  as  it 
reached  beyond  this  level,  the  food  was  promptly  separated  and 
carried  slowly  into  the  stomach.  There  was  no  evidence  of 
obstruction  at  the  cardia.  For  further  assurance  the  animal  was 
etherized,  the  right  vagus  also  severed  in  the  neck,  the  left 
thoracic  wall  widely  opened,  and  the  oesophagus  watched  directly, 
as  water  was  introduced  through  a  tube  into  the  cervical  portion. 
Where  the  vessels  of  the  left  lung  crossed  the  gullet,  peristaltic 
waves  appeared,  and  moved  slowly  downward  until  they  went 
out  of  sight  behind  the  diaphragm.  The  point  where  the  waves 
were  first  seen  was  marked  by  making  a  deep  cut,  and  the  animal 
was  then  killed.  The  oesophagus  of  the  rabbit  longest  observed 
and  the  oesophagus  of  the  monkey  received  careful  histological 
examination.  Striped  muscle,  almost  exclusively,  was  seen 
throughout  the  length  of  the  rabbit's  oesophagus.  The  part 
of  the  monkey's  oesophagus  above  the  cut — the  part  which  was 
paralyzed — was  composed  entirely  of  striped  fibres  ;  the  part 
below  the  cut  had  only  a  few  scattered  striped  fibres,  the  rest 
was  all  smooth  muscle. 

Mosso's  observations  revealed  an  cesophageal  peristalsis  of 
central  origin,  distinguished  by  Meltzer  as  primary  peristalsis. 
Wild's  studies  disclosed  a  reflex  oesophageal  peristalsis  of 
peripheral  origin,  the  secondary  peristalsis  of  Meltzer.  To  these 
two  varieties,  which  require  vagus  support,  must  be  added  a 
third,  which  can  be  seen  when  a  portion  of  the  oesophagus  is 
supplied  with  smooth  muscle.  The  peristalsis  of  this  portion, 


THE   NERVOUS    CONTROL   OF   DEGLUTITION  31 

like  peristalsis  below  the  cardia,  is  capable  of  autonomy.  In 
many  cases  which  I  have  observed,  it  has  been  sufficient  without 
vagus  support  to  clear  the  oesophagus  of  any  ordinary  food 
which  had  been  carried  into  the  thoracic  segment.  And,  as  we 
have  already  noted,  the  rapid  contraction  of  the  muscles  of 
the  mouth  are  able  to  discharge  fluid  food  into  this  region,  where 
independent  peristalsis  is  possible. 


REFERENCES. 

1  Oppel,  Lehrb.  d.  Vergl.  Mik.  Anat.,  1898,  ii.,  pp.  142,  146. 

2  Kahn,  Arch.  f.  Physid.,  1903,  SuppL,  p.  386. 

3  Wassilieff,  Ztsch.  f.  Bid.,  1888,  xxiv.,  pp.  39,  40. 

4  Marckwald,  Ztschr.  f.  Bid.,  1889,  xxv.,  p.  46. 

5  Kahn,  Arch.  f.  Physid.,  1906,  p.  361. 

6  Wild,  Ztschr.  f.  rat.  Med.,  1846,  v.,  pp.  101,  113. 

7  Meltzer,  Amer.  J.  Physiol. ,  1899,  ii.,  p.  270. 

8  Meltzer,  Zentralbl.  /.  Physiol.,  1905,  xix.,  p.  995  ;  Proc.  Soc.  Exper.  Biol. 
M.,  New  York,  1907,  iv.,  p.  35. 

9  Kronecker  and  Meltzer,  Monatsber.  d.  konigl.  preussisch.  Akad.   d.  Wis- 
sensch.  zu  Berlin,  1881,  p.  100. 

10  Meltzer,  Am.  J.  Physid.,  1899,  ii.,  p.  266. 

11  Starling,  Recent  Advances  in  the  Physidogy  of  Digestion,  Chicago,  1906, 
p.  132. 

12  Meltzer,  Zentralbl.  f.  Physid.,  1905,  xix.,  p.  994. 

13  Reid,  Edinb.  M.  and  8.  J.,  1839,  Ii.,  p.  274. 

34  Volkmann,  Wagner's  Handworterb.  d.  Physid.,  1844,  ii.,  p.  586. 

15  Cannon,  Am.  J.  Physid.,  1906,  xvii.,  p.  429. 

16  Cannon  and  Murphy,  Ann.  Svrg.,  1906,  xliii.,  p.  522. 


CHAPTER  IV 

CONDITIONS  AFFECTING  THE  ACTIVITIES  OF  THE  CARDIA 

THE  thickened  band  of  circular  smooth  muscle  at  the  junction  of 
the  oesophagus  with  the  stomach — the  cardiac  sphincter,  or 
cardia — has  the  function  of  preventing  the  passage  of  material 
from  the  stomach  back  into  the  oesophagus.  Normally  we  are 
quite  unconscious  of  the  nauseating  odour  and  the  highly  dis- 
agreeable taste  of  the  gastric  contents,  and  for  this  pleasant 
security  the  closed  cardia  is  largely  responsible.  As  aids  in  estab- 
lishing the  barrier  between  the  stomach  and  the  gullet,  the  sharp 
angle  between  the  two  structures,  acting  like  a  valve,  and  the 
close  grasp  of  muscle  layers  in  the  diaphragm,  have  been  men- 
tioned.1 Evidence  will  indicate,  however,  that  these  accessory 
agencies  must  be  regarded  as  relatively  insignificant  compared 
with  the  tonus  of  the  sphincter. 

That  the  cardia  is  normally  closed  has  been  observed  in  various 
ways ; — by  introducing  a  finger  into  the  oasophagus  from  the  opened 
stomach,  by  direct  inspection  from  below,  and  by  inspection  from 
above  through  an  oesophagoscope.  The  closed  condition  can  also 
be  inferred  from  the  stoppage  of  swallowed  liquids  in  the  lower 
gullet  until  a  peristaltic  wave  arrives  and  presses  them  through. 
Although  the  contracted  state  of  the  sphincter  seems  continuous, 
it  is  capable  of  exhibiting  an  alternating  increase  and  decrease — 
a  phenomenon  known  to  Magendie  early  in  the  last  century.2 
Two  activities  of  the  cardiac  sphincter,  therefore,  are  to  be  dis- 
tinguished-^-a  persistent  contracted  state  or  tonus,  and  at  times, 
superposed  on  this,  rhythmic  alternation  of  contraction  and  re- 
laxation. In  these  two  manifestations  the  smooth  muscle  of  the 
cardia  is  like  the  smooth  muscle  of  other  parts  of  the  alimentary 
canal,  to  be  considered  later. 

The  tonic  contraction  is  itself  variable  in  intensity,  and  can  be 
increased  or  decreased  by  a  number  of  conditions.  Usually,  in  a 


CONDITIONS    AFFECTING  THE    CARDIA  33 

state  of  rest,  the  tonus  is  not  high.  The  common  ease  of  passage 
through  the  sphincter  has  been  observed  by  several  investigators. 
Mosso  noted  that  a  small  wooden  ball,  attached  to  a  thread, 
could  be  withdrawn  from  the  stomach  without  meeting  any  con- 
siderable resistance.3  On  the  cesophageal  side,  v.  Mikulicz 
observed  in  man  that  such  slight  pressure  as  2  to  7  centimetres  of 
water  was  sufficient  to  drive  air  or  water  into  the  stomach.  As 
a  rule  the  necessary  pressure  was  less  than  that  of  a  column  of 
fluid  which  would  fill  the  thoracic  oesophagus.4 

As  already  stated,  a  sound  can  be  heard  by  listening  over  the 
region  of  the  cardia,  six  or  seven  seconds  after  liquids  have  been 
swallowed.  This  sound  is  due  to  the  swallowed  material,  liquid 
and  air.  being  pressed  through  the  tonically  contracted  sphincter. 
Sometimes  this  sound  is  heard  immediately  after  swallowing — a 
result  which  Meltzer  has  attributed  to  a  weakly  contracted 
cardia,  because,  among  other  reasons,  he  observed  it  in 
consumptives  who  easily  regurgitated  gastric  contents  while 
coughing.5 

Even  the  slight  contraction  that  normally  prevails  in  the  resting 
cardia  can  be  reduced  by  nervous  influences.  During  repeated 
deglutition,  for  example,  the  sphincter  becomes  more  and  more 
relaxed  as  the  number  of  swallows  increases,  and  may  be  so  com- 
pletely relaxed  that  no  sounds  are  heard  as  the  fluid  passes  through 
into  the  stomach.6  In  the  rabbit  with  opened  abdomen  the  cardia 
can  be  seen  to  enlarge  slightly  with  each  swallowing  "movement : 
and  if  the  stomach  is  filled  with  air,  an  act  of  deglutition  is  accom- 
panied by  the  release  of  air  into  the  oesophagus  through  the 
patulous  sphincter.  As  the  peristaltic  wave  descends,  it  pushes 
the  air  downward,  and  only  when  the  escaped  volume  is  restored 
to  the  stomach  does  the  cardia  close.  This  relaxation  of  the 
terminal  sphincter  as  a  peristaltic  wave  approaches  admirably 
illustrates  the  general  law  that  opposed  muscles  normally  act,  not 
in  opposition,  but  in  harmony — a  law  that  Meltzer  emphasized 
in  this  connection.7 

Following  the  relaxation  of  the  cardia  and  the  passage  of  the 
swallowed  bolus,  there  is  a  prompt  contraction.  This  contrac- 
tion, as  Kronecker  and  Meltzer  observed,  is  much  more  intense 
and  lasts  longer,  the  longer  the  series  of  swallowing  movements 
that  have  preceded. 

The  nervous  path  by  which  the  cardia  is  affected  in  the  process 
of  swallowing  is  by  way  of  the  vagi.  Impulses  along  these  nerves 


34  THE   MECHANICAL   FACTORS    OF   DIGESTION 

cause,  not  only  the  relaxation  of  the  sphincter,  but  also  the  sub- 
sequent increase  of  tone.  The  two  effects  can  be  separated  by 
varying  the  rate  and  intensity  of  stimulation.8  During  vagus 
stimulation  in  the  neck  region  Langley  observed  relaxation,  and 
when  stimulation  ceased,  strong  contraction  of  the  sphincter. 
By  giving  small  doses  of  atropine,  he  was  able  to  eliminate  the 
motor  fibres  and  produce  pure  inhibitory  effects.9  Langley10  has 
also  reported  that  the  cardiac  sphincter  is  relaxed  when  adrenalin 
is  given  ;  and  as  the  effect  of  adrenalin  is  an  indicator  of  the 
presence  and  function  of  sympathetic  nerve  fibres,  the  conclusion 
is  justified  that  the  cardia  has  a  sympathetic  supply  which  causes 
relaxation. 

I  have  already  stated  that  severance  of  both  vagus  nerves 
causes  in  the  cat  a  temporary  increase  of  tone  in  the  cardiac 
sphincter  (see  p.  29).  This  observation  is  in  accord  with  the 
observations  of  Bernard,11  Schiff,12  and  Kronecker  and  Meltzer,13 
that  cutting  both  vagi  in  the  neck  is  soon  followed  by  strong 
contraction  of  the  lowest  part  of  the  oesophagus.  But  they  are 
not  in  accord  with  the  observations  of  Krehl,14  that  after  vagus 
section  the  cardia  is  patulous  ;  nor  are  they  in  accord  with  Katsch- 
kowsky's15  assumption  to  the  same  effect.  It  may  be  that  this 
conflict  of  evidence  can  be  explained  by  the  temporal  factor. 
Thus  Sinnhuber16  concludes,  from  a  critical  review  of  the  litera- 
ture and  from  his  own  experiments,  that,  though  cutting  the  vagi 
may  cause  the  cardia  to  enter  a  cramp-like  contraction,  this  is 
only  a  temporary  state.  Starck17  also  does  not  believe  that  vagus 
section  produces  any  lasting  hindrance  to  the  passage  of  food 
through  the  cardia.  In  my  experience,  the  increased  tonus  of 
the  cat's  cardia  after  bilateral  vagotomy  usually  does  not  persist 
as  a  considerable  obstacle,  and  the  forcing  of  food  into  the 
stomach  by  cesophageal  peristalsis  becomes  in  time  not  difficult. 
But  there  have  been  a  few  instances  in  which  there  was  continued 
trouble  in  passing  a  tube  into  the  stomach ;  the  oesophagus  in 
these  cases  suffered  a  marked  dilatation,  and  became  filled  with 
food  which  was  not  removed. 

Other  conditions  affecting  the  tonic  contraction  of  the  cardia 
have  been  reported  by  v.  Mikulicz.18  For  example,  in  his  obser- 
vations on  a  patient  he  noted  that,  when  the  region  of  the  cardia 
had  been  irritated  mechanically  or  chemically,  the  pressure  re- 
quired to  force  fluid  into  the  stomach  was  increased.  It  was 
higher  for  cold  drinks  and  for  carbonated  water  than  for  warm 


CONDITIONS    AFFECTING   THE    CARDIA  35 

water.*  These  differences  in  resistance  to  the  passage  of  different 
fluids  through  the  cardia  were  seen  also  in  the  dog,  but  they 
disappeared  when  the  vagi  were  cut. 

From  the  stomach  side  the  passage  of  air  into  the  oesophagus 
occurs  by  eructation,  according  to  Kelling,19  whenever  intragastric 
pressure  rises  to  about  25  centimetres  of  water.  A  still  easier 
regurgitation  is  indicated  by  the  observation  of  Kronecker  that 
when,  after  repeated  "  empty  "  swallowings,  the  dog's  stomach 
has  been  rilled  with  air,  the  least  motion  suffices  to  cause  the  air 
to  pass  back  into  the  oesophagus.20  Deep  anaesthesia,  in  Kelling's 
experience,  abolishes  this  ready  relaxation  of  the  sphincter,  and 
then  the  stomach  may  be  inflated  to  bursting  before  the  air  will 
escape. 

Most  of  the  evidence  thus  far  presented  indicates  a  relatively 
low  degree  of  tonic  contraction  of  the  cardiac  ring.  This  con- 
dition is  not  one  that  assures  the  retention  of  gastric  contents  in 
the  stomach  during  digestion,  which  is  the  normal  function  of 
the  sphincter.  As  we  shall  see,  however,  a  special  local  and  auto- 
matic arrangement  exists  by  which  the  cardia  is  more  firmly 
closed  while  gastric  digestion  is  in  progress.  Before  regarding 
this  mechanism  for  locking  the  food  in  the  stomach,  we  must 
consider  the  second  activity  of  the  cardia  previously  mentioned — 
its  rhythmic  contractions. 

The  rhythmic  oscillations  in  the  contraction  of  the  cardia,  as 
already  stated,  were  known  to  Magendie  nearly  a  century  ago. 
These  variations  of  contraction,  according  to  Schiff,  are  not  actu- 
ally localized  at  the  cardia,  but  result  from  a  ring  of  constriction 
moving  up  and  down  the  lower  oesophagus  and  periodically  in- 
volving the  cardia.21  Schiff 's  observations  were  made  on  dogs 
and  cats.  In  1860,  Basslinger  described  rhythmic  pulsations  of 
the  cardia  in  the  excised  stomach  of  the  rabbit,22  a  phenomenon 
sometimes  designated  as  "  Basslinger's  pulse."  The  cardia  of  the 
normal  rabbit  Kronecker  and  Meltzer23  found  usually  quiet,  but 
in  a  freshly  bled  rabbit  they  saw  the  spontaneous  movements 
described  by  Basslinger. 

If  Schiff's  conception  of  peristalsis  and  antiperistalsis  in  the 

*  In  this  connection  the  observation  by  Kronecker  and  Meltzer  (Arch.  /. 
PhysioL,  1883,  Suppl.,  p.  355)  may  be  cited,  that  carbonated  water  produces 
strong  persistent  spasm  of  the  oesophagus,  which  cannot  be  inhibited  by  subse- 
quent deglutition.  This  peculiar  effect  they  did  not  investigate  further.  A 
distressing  cramp  is  at  times  experienced  in  the  region  of  the  cardia,  which  is 
at  once  relieved  when  accumulated  gases  are  released  from  the  stomach.  The 
observations  may  be  significant  in  relation  to  cardiospasm. 


36  THE   MECHANICAL   FACTORS    OF   DIGESTION 

lower  oesophagus  is  correct,  any  regurgitation  of  gastric  contents 
could  take  place  only  slowly  and  to  a  slight  extent ;  but  if,  as 
Magendie  stated,  a  true  diminution  of  the  contracted  state  occurs, 
leaving  an  easily  forced  passage,  gastric  contents  might  be  forced 
backward  suddenly  and  throughout  the  gullet.  The  difference 
between  the  views  of  Magendie  and  Schiff,  and  the  possibility 
that,  after  all,  their  and  Basslingers  observations  might  have 
resulted,  as  Kronecker  and  Meltzer's  study  suggests,  from  ab- 
normal conditions,  made  it  desirable  to  investigate  the  action  of 
the  cardia  under  more  natural  conditions. 

In  1902,  during  an  attempt  to  see  the  movement  of  particles 
of  food  in  the  stomach  when  the  gastric  contents  were  fluid, 
I  noted  repeated  regurgitation  from  the  stomach  into  the 
oesophagus.24  The  fluid  consisted  of  100  c.c.  of  thin  starch  paste 
mixed  with  5  grammes  of  subnitrate  of  bismuth.  It  was  given 
by  stomach-tube.  The  animal  lay  comfortably  on  a  holder, 
unanaesthetized,  and  was  examined  by  means  of  the  X  rays.  The 
regurgitation  was  unattended  by  any  signs  of  nausea  or  retching, 
and  when  the  animal  was  lifted  from  the  holder  she  acted  quite 
as  a  cat  normally  acts.  The  periodically  lessened  contraction  of 
the  cardia  would  therefore  appear  to  be  a  natural  phenomenon. 
Since  the  fluid,  on  emerging  from  the  stomach,  at  once  passed 
quickly  up  the  oesophagus  to  the  level  of  the  heart,  or  even  to  the 
base  of  the  neck,  it  is  clear  that  Magendie 's  conception  was  correct, 
and  that  SchifFs  idea  of  an  oscillating  peristalsis  and  antiperistalsis 
in  the  lower  oesophagus  must  be  discarded.  In  fact,  no  one  who 
has  studied  the  oesophagus  directly  has  ever  seen  antiperistaltic 
waves  in  it. 

Each  regurgitation,  as  I  watched  them,  was  followed  at  once 
by  a  peristaltic  wave  which  pushed  the  escaped  material  back 
again  into  the  stomach.  Soon  after  it  was  thus  restored,  the 
cardia  again  relaxed  and  it  again  rushed  out,  only  to  be  restored 
to  the  stomach  by  another  peristaltic  wave.  Thus  the  process 
continued.  The  peristaltic  wave  was  seldom  started  by  volun- 
tary deglutition,  but  was  of  the  secondary  order,  stimulated  by 
the  presence  of  the  material  in  the  oesophagus. 

Kegurgitation  and  restoration  of  the  fluid  may  thus  recur 
fairly  periodically  for  twenty  or  thirty  minutes.  The  periods  are 
shorter  at  first  than  later.  In  the  following  figures  are  shown 
the  time  taken  by  these  periodic  movements  when  a  large  cat  was 
given  180  c.c.  of  fluid  boiled  starch  at  3.20  p.m.  The  figures 


CONDITIONS    AFFECTING   THE    CARDIA  37 

under  "  Out  "  indicate  the  moment  when  the  fluid  emerged  into 
the  oesophagus  ;  those  under  "In,"  when  the  last  of  the  fluid 
disappeared  into  the  stomach. 

Out,  In.  Out.  In. 

3-21—  6  3-21—12  3-22—19  3-22—28 

17  24  44  51 

32  38  23—  2  23—  8 

48  54  21  29 

22—  2  22—  8  43  49 

The  regurgitation  continued  thus,  but  became  gradually  less 
frequent.  Twenty  minutes  after  the  first  observation,  appearance 
and  disappearance  were  as  follows  : 

Out.  In. 

3-41—14  3-41—27 

42—26  42—42 

43—45  43—59 

45—  8  45—16 

During  the  eighteen  minutes  of  observation  that  followed,  the 
food  emerged  only  three  times. 

In  this  instance  there  was  a  fairly  rhythmic  appearance  of  food 
in  the  oesophagus,  beginning  at  the  rate  of  four  times  a  minute, 
gradually  falling  to  three  and  two  times  a  minute,  and  ceasing 
almost  entirely  soon  after  a  rate  of  about  once  per  minute  was 
reached. 

Two  questions  are  suggested  by  these  observations  :  Under 
what  circumstances  do  the  regurgitations  occur  ?  and,  Why, 
once  begun,  do  they  cease  ? 

In  answer  to  the  first  question-,  the  fluidity  of  the  gastric  con- 
tents must  be  regarded  as  a  prime  factor  in  the  regurgitations. 
When  the  food  escapes  into  the  oesophagus,  it  escapes  quickly  in 
a  thin  stream.  If  the  stomach  is  full  of  more  or  less  gross  frag- 
ments of  food,  it  is  quite  conceivable  that  a  slight  weakening  of 
the  contraction  of  the  cardia  would  not  permit  such  semi-solid 
material  to  pass.  A  second  factor  in  the  regurgitation  is  intra- 
gastric  pressure.  Into  the  stomach  of  the  cat  that  furnished  the 
records  given  above  was  introduced  on  one  occasion  60  c.c.  of 
the  fluid  starch,  with  no  regurgitation  during  the  next  five 
minutes  ;  60  c.c.  more  was  introduced,  with  no  regurgitation  during 
the  five  minutes  that  followed  ;  then  60  c.c.  more  was  introduced, 
making  in  all  180  c.c.,  and  regurgitations  at  once  began  and  con- 
tinued. In  order  to  demonstrate  the  rhythmic  relaxations  of  the 
cardia,  therefore,  the  gastric  contents  must  be  fluid,  and  must 


38  THE   MECHANICAL   FACTORS    OF   DIGESTION 

be  under  sufficient  pressure  to  pass  through  the  cardia  when  its 
contraction  weakens. 

At  first  it  seemed  that  fluidity  and  pressure  were  the  only 
factors  concerned.  The  cessation  of  the  regurgitations  might 
then  be  explained  by  a  slow  accommodation  of  the  stomach  to 
the  volume  of  its  contents,  or  by  the  escape  of  material  into  the 
duodenum  until  the  intragastric  pressure  was  insufficient  to  press 
the  fluid  through  the  only  slightly  relaxed  cardia.  These  explana- 
tions, however,  are  not  adequate.  Kelling  has  shown  that, 
within  limits,  intragastric  tension  is  readily  adjusted  to  varying 
amounts  of  food,  and  that  for  this  adjustment  only  a  few  moments 
are  required  ;25  the  normally  rapid  adjustment  of  intragastric 
tension,  therefore,  would  not  explain  the  cessation  of  the  regurgita- 
tions after  their  continuance  for  twenty  or  thirty  minutes.  And 
observations  on  the  intestinal  contents  of  animals  in  which  the 
regurgitations  have  ceased  have  shown  only  a  small  amount  of 
the  fluid  starch  in  the  intestine.  A  diminution  of  intragastric 
pressure  does  not,  therefore,  account  for  the  disappearance  of  the 
regurgitations. 

Since  the  repeated  escape  of  fluid  food  into  the  oesophagus 
is  dependent  on  a  periodic  lessening  of  the  contraction  of  the 
cardia  and  on  an  intragastric  pressure  sufficient  to  force  the 
gastric  contents  through  the  weakened  barrier,  and  since  intra- 
gastric pressure  probably  does  not  materially  diminish  at  the 
time  when  the  regurgitations  cease,  the  explanation  of  the 
cessation  must  lie  in  a  change  at  the  cardia.  Either  the  rhythmic 
relaxations  might  be  stopped,  or  the  tonus  of  the  sphincter  might 
be  increased.  With  an  increased  tonus  the  cardia  might,  of 
course,  still  undergo  rhythmic  contractions  and  relaxations,  but 
on  a  level  so  much  higher  than  before  that  the  intragastric 
pressure  would  now  be  unable  to  overtop  it.  Thus  the  cardia 
would  perform  its  normal  function  of  preventing  the  passage  of 
food  backward  into  the  oesophagus  during  the  process  of  gastric 
digestion. 

What  new  conditions  developed  in  the  stomach  during 
digestion  might  affect  the  cardia  ?  The  conditions  might  be 
of  two  orders,  mechanical  or  chemical :  the  actual  stretching 
of  the  stomach  might  cause  closure  of  the  cardia,  as  Magendie 
suggested  ;  or  the  new  secretion  poured  out  by  the  stomach 
during  digestion  might,  with  its  acid  reaction,  have  that  effect. 
As  we  have  learned,  the  rhvthmic  relaxations  of  the  cardia  are 


CONDITIONS    AFFECTING  THE    CARDIA  39 

made  manifest  only  as  the  content  of  the  stomach  is  increased. 
And,  furthermore,  the  gastric  wall  does  not  become  more  stretched 
by  any  material  increase  of  the  contents,  as  the  food  lies  in  the 
stomach  during  twenty  or  thirty  minutes.  The  stopping  of  the  re- 
gurgitations  is  therefore  not  explained  by  increase  of  intragastric 
pressure.  Is  the  chemical  agency,  acid  in  contact  with  the  gastric 
mucosa,  capable  of  changing  the  contraction  of  the  sphincter  ? 

Evidence  will  be  presented  later  showing  that,  if  acid  is  con- 
tinuously injected  into  the  duodenum  close  beyond  the  pylorus, 
that  sphincter  can  be  kept  closed  for  an  unlimited  period. 
Indeed,  this  response  of  the  pylorus  to  the  acid  illustrates  a 
general  law  of  the  alimentary  tract,  that  a  stimulus  causes  a 
contraction  above  the  stimulated  point.  And  just  as  acid 
beyond  the  pylorus  keeps  the  pylorus  closed,  so  likewise  acid 
in  the  stomach  (beyond  the  cardia)  may  keep  the  cardia  closed. 
Thus  an  essential  condition  for  digestion  in  the  stomach,  the 
presence  of  acid,  would  itself  automatically  hold  a  barrier  against 
a  return  of  the  contents  into  the  oesophagus. 

That  a  marked  acidity  of  the  gastric  contents  does  promptly 
check  regurgitation  through  the  cardia  is  proved  by  such  ob- 
servations as  the  following  : 

A  cat  with  an  empty  stomach  was  given  by  stomach-tube 
200  c.c.  fluid  starch  with  10  grammes  bismuth  subnitrate  at 
2.55  p.m.  The  regurgitations  occurred  as  follows  : 

Out.  In.  Out  In. 

2-56—  1  2-56—11  2-58—38  2-58—49 

16  28  58  59—10 


32  42 

46  •  57 

57—  8  57—18 


59—30  40 

(cat  excited) 
3-00—35  3-01—  2 


(cat  excited) 

29                              39                          01—15  25 

48                              60                                  44  54 

58—12                      58—22                          02—  2  02—12 

At  this  time  no  food  had  passed  through  the  pylorus.  The 
contents  of  the  stomach  were  now  as  much  as  possible  removed 
(about  180  c.c. ).  The  reaction  was  very  faintly  acid.  Fresh  fluid 
starch  was  added  to  make  200  c.c.,  and  then  4  c.c.  of  25  per  cent, 
hydrochloric  acid  was  mixed  with  the  fluid,  making  approxi- 
mately a  0-5  per  cent,  acidity,  which  is  normal  for  carnivora. 
The  fluid  was  then  reintroduced  into  the  same  animal  at 
3.12  p.m.,  with  the  following  results  : 

Out.  In. 

3.13 — 45  3-13—53 

14—17  14—39 


40  THE   MECHANICAL   FACTORS    OF  DIGESTION 

The  fluid  passed  from  the  stomach  into  the  oesophagus  these 
two  times  in  a  very  thin  stream.  Thereafter  there  was  no 
regurgitation  whatever  during  ten  minutes  of  observation. 
The  cardia  was  now  holding  tightly  enough  to  retain  gastric 
contents  amounting  to  220  c.c.,  although  previous  to  the  acidifi- 
cation it  did  not  withstand  the  pressure  of  200  c.c. 


This  observation  has  been  repeated  on  normal  animals  and 
on  an  animal  whose  splanchnic  nerves  had  previously  been 
severed,  with  the  same  results. 

The  effect  of  acid  in  the  stomach  on  the  tonus  of  the 
cardia  can  be  demonstrated  also  in  the  anaesthetized  operated 
animal. 

A  cat  was  etherized  and  also  given  subcutaneously  1  c.c. 
of  1  per  cent,  morphine  sulphate  in  order  to  maintain  uniform 
anaesthesia.  When  the  animal  was  thoroughly  anaesthetized, 
the  spinal  cord  was  pithed  below  the  brachial  region,  the  stomach 
exposed,  and  a  tube  tied  into  the  cardiac  end  by  means  of  a 
ligature  encircling  the  organ.  Another  tube  was  introduced 
through  the  cervical  oesophagus  as  far  as  the  upper  thorax,  and 
tied  in  place.  Each  tube  was  connected  by  rubber  tubing  with 
a  long  upright  thistle  tube.  Warm  physiological  salt  solution 
was  now  introduced  until  the  level  in  each  tube  was  9  centi- 
metres above  the  cardia.  At  once  the  fluid  in  the  resophageal 
tube  began  to  disappear  and  reappear  at  fairly  regular  intervals, 
precisely  as  in  the  X-ray  observations  on  regurgitation. 

After  the  rhythmic  regurgitation  had  proceeded  for  several 
minutes  the  salt  solution  was  removed.  It  was  replaced  by  a 
similar  solution  containing  0'5  per  cent,  hydrochloric  acid, 
poured  into  the  thistle  tube  connected  with  the  stomach.  The 
acidulated  salt  solution  was  added  until  it  rose  19  centimetres 
above  the  cardia.  For  several  minutes  it  stood  at  that  point, 
with  no  relaxation  of  the  sphincter.  The  stomach  was  now 
compressed,  and  the  fluid  rose  33  centimetres  above  the  cardia 
before  the  sphincter  relaxed.  The  fluid  that  then  passed  into 
the  03sophagus  was  immediately  pushed  back  into  the  stomach 
by  peristalsis  and  held  there.  Pressure  again  applied  to  the 
stomach  forced  the  column  of  salt  solution  to  42  centimetres 
above  the  cardia  before  relaxation  again  occurred.  No  rhythmic 
regurgitation  was  observed. 

Now  the  acidulated  salt  solution  was  removed  from  the 
stomach  and  replaced  by  1  per  cent,  sodium  bicarbonate,  poured 
into  the  stomach-tube  until  9  centimetres  above  the  cardia. 
Almost  immediately  regurgitations  began,  and  continued 
rhythmically  during  ten  minutes  of  observation. 


CONDITIONS    AFFECTING   THE    CARDIA  41 

The  closure  of  the  cardia  by  intragastric  acidity  can  be 
registered  graphically  by  connecting  the  oesophageal  tube, 
described  in  the  foregoing  experiment,  with  a  recording  tambour. 
The  regurgitations  into  the  oesophagus  cause  the  writing  lever 
of  the  tambour  to  rise,  and  as  the  regurgitated  fluid  is  carried 
back  into  the  stomach  the  lever  falls.  Fig.  1  presents  a  record 
of  such  regurgitations.  The  glass  tube  tied  into  the  cardiac 
end  of  the  stomach  was  short,  and  connecting  it  with  a  thistle 
tube  was  a  piece  of  rubber  tubing.  Through  the  rubber  tubing 
a  hollow  needle  was  introduced  into  the  gastric  cavity.  Thus 
the  stomach  was  not  disturbed  in  the  subsequent  experimental 
manipulation.  During  the  period  indicated  by  the  broad  black 
line  at  A,  sufficient  hydrochloric  acid  (2  c.c.)  was  introduced 


FIG.  1. — RECORD  SHOWING  CESSATION  OF  RHYTHMIC  REGTJRGITATIONS  OF 
FLUID  FROM  THE  STOMACH  INTO  THE  (ESOPHAGUS  ON  ACIDULATION  OF 
GASTRIC  CONTENTS. 

The  upstroke  of  the  larger  oscillations  represents  the  outflow,  and  the  down- 
stroke  the  return  of  the  fluid  to  the  stomach  by  oesophageal  peristalsis. 
The  small  oscillations  are  due  to  respiration.  The  time  is  marked  in  half- 
minute  intervals. 

through  the  needle  into  the  stomach  to  render  the  salt  solution  acid 
to  0-5  per  cent.  After  one  more  regurgitation  the  cardia  closed. 
The  question  now  arises  as  to  whether  the  effect  of  the  acid 
on  the  cardia  is  a  local  effect,  or  mediated  through  the  vagus  or 
splanchnic  nerves.  That  regurgitations  continue  after  splanchnic 
section,  and  may  be  caused  to  stop  by  rendering  the  gastric 
contents  acid,  has  already  been  noted.  The  task  of  eliminating 
the  vagus  nerves  is  more  difficult,  because,  as  we  have  learned, 
only  the  lowest  few  centimetres  of  the  oesophagus  remain  capable 
of  peristalsis  after  vagotomy,  and  this  portion  did  not  give 
clear  records  of  a  restoration  of  regurgitated  fluid  into  the 
stomach.  The  effect  of  the  acid  can  be  tested,  however,  by 
observing  the  intragastric  pressure  required  to  open  the  cardia 
before  and  after  the  acidulation  of  the  fluid. 

A  cat  with  the  vagus  nerves  severed  several  days  previously 
was  prepared  for  observation  in  the  manner  above  described. 


42  THE   MECHANICAL   FACTORS    OF   DIGESTION 

Warm  salt  solution  was  poured  into  the  thistle  tube  connected 
with  the  stomach  until  the  pressure  was  14  centimetres,  rising 
to  19  centimetres  during  inspiration.  Only  then  did  the  cardia 
relax.  A  second  determination  resulted  in  the  same  figures. 

The  salt  solution,  which  proved  to  be  neutral,  was  now  re- 
moved and  replaced  by  the  same  solution  containing  0'5  per 
cent,  hydrochloric  acid.  The  acid  fluid  was  poured  into  the 
tube  tied  into  the  stomach  until  the  pressure  was  17  centimetres 
(rising  to  22  centimetres  during  inspiration)  before  the  cardia 
relaxed.  The  fluid  was  now  removed  and  immediately  again 
poured  into  the  stomach  ;  this  time  the  pressure  rose  to  1 9  centi- 
metres (24  and  25  centimetres  during  inspiration)  before  the 
cardia  opened.  Another  immediate  repetition  gave  21  centi- 
metres rising  to  26  and  27  centimetres,  as  threshold  pressures. 
In  a  fourth  trial  the  pressure  was  raised  to  53  centimetres,  and 
the  sphincter  gave  way  only  when  still  more  fluid  was  poured 
into  the  tube. 

In  this  experiment,  as  well  as  in  those  in  which  regurgitations 
were  observed  and  registered,  a  more  or  less  prolonged  latent 
period  intervened  between  the  application  of  the  acid  and  its 
full  effect  in  closing  the  cardia.  But  the  fact  that  the  liminal 
pressure  gradually  rose  in  this  instance,  and  finally  became 
almost  four  times  as  great  with  acid  gastric  contents  as  it  was 
with  neutral  gastric  contents,  proves  that  the  effect  of  the  acid 
is  not  produced  through  extrinsic  nerves,  but  by  the  local  reflex 
in  the  wall  of  the  gut.  This  result  has  been  confirmed  by  similar 
observations  made  immediately  after  pithing  the  lumbar  and 
thoracic  cord  and  severing  the  vagus  nerves. 

Does  not  the  prolonged  period  of  regurgitation  observed 
when  fluid  starch  was  given  (frequently  twenty  or  thirty  minutes 
after  its  introduction)  indicate  that  the  acid  mechanism  of  the 
cardia  is  rather  defective  ?  In  considering  this  question,  we  should 
remember  that  boiled  starch  has  very  little  effect  in  exciting 
the  flow  of  gastric  juice,26  and  that  the  cardia  therefore  probably 
exhibits  relaxations  for  a  much  longer  period  when  fluid  starch 
is  given  than  when  foods  more  favourable  to  gastric  secretion 
are  fed. 

The  fluid  character  of  the  boiled  starch  is  also  unfavourable 
to  the  early  closure  of  the  cardia,  for  the  acid  secreted  is  not 
kept  in  contact  with  the  wall  of  the  stomach,  but  is  diffused 
into  the  fluid  ;  and  each  movement  of  the  fluid  to  and  fro  between 
stomach  and  oesophagus  serves  to  mix  the  secreted  acid  with 


CONDITIONS    AFFECTING  THE    CARDIA  43 

the  total  contents.  For  this  reason  it  was  impossible  to  get 
consistent  results  in  attempting  to  determine  the  acidity  of  the 
gastric  contents  under  these  circumstances.  When  the  food  is 
less  fluid,  the  acid  reaction  of  the  contents  of  the  cardiac  end  of 
the  stomach  is  found  solely  on  the  surface,  near  the  mucosa,  for 
a  considerable  period  after  digestion  has  commenced.  Under 
these  circumstances  the  conditions  for  closure  of  the  cardia  are 
most  favourable. 

A  return  of  material  from  the  stomach  to  the  oesophagus  in 
dogs  has  been  reported  by  Kast.27  Lycopodium  spores  intro- 
duced through  a  gastric  fistula  into  the  stomach  often  appeared 
after  half  an  hour  at  an  oesophageal  fistula  in  the  neck.  This 
reversed  movement  of  material  in  the  oesophagus  was  not 
attended  by  any  retching  or  vomiting.  To  test  whether  this 
return  from  the  stomach  might  be  true  of  human  beings,  eleven 
patients  were  given,  after  supper,  lycopodium  spores  carefully 
enclosed  in  a  gelatine  capsule.  As  a  further  precaution,  the 
capsule  was  enveloped  in  a  wafer,  and  was  then  quickly  swal- 
lowed with  the  aid  of  water.  In  six  of  the  eleven  cases  spores 
were  found  in  the  mouth  washings  next  morning,  and  in  none 
of  these  were  any  spores  found  in  mouth  washings  taken  one 
or  two  hours  after  the  capsule  was  swallowed.  It  is  altogether 
probable  that  in  the  positive  cases  the  cardia  must  have  relaxed 
to  permit  the  exit  of  material  into  the  oesophagus.  Thereafter 
the  fluids  bearing  the  very  fine  seeds  may  have  been  slowly 
spread  toward  the  mouth  by  alterations  of  pressure  due  to 
respiration  and  the  heart-beat,  much  as  swallowed  material  is 
spread  through  the  paralyzed  gullet.  Indeed,  with  a  weakened 
cardia,  the  descending  diaphragm,  by  pressing  on  the  stomach 
while  lessening  intrathoracic  pressure,  could  pump  fluid  from 
the  stomach  towards  the  mouth.  Kast  suggests  that  the  dis- 
agreeable taste  and  the  coating  of  the  tongue  in  gastric  dis- 
turbance may  result  from  the  adhesion  to  its  rough  surface  of 
partly  digested  bits  of  food,  leucocytes  and  epithelial  cells  that 
have  come  back  from  the  stomach.  This  suggestion  gains 
interest  in  connection  with  our  discussion  of  the  acid  closure  of 
the  cardia,  for  the  coated  tongue  appears  especially  in  cases  of 
abnormal  fermentation  of  gastric  contents  which  results  from 
deficient  hydrochloric  acid.  This  is  preciselv^feJte^c^njdi^ion  for 
a  relaxed  cardia. 

Although  the  evidence  points  to  the  acid^onTyofp^e^  t-dj& 


R 

^2^*&tMWffii,  1 1  (V  '<e 

4fe^ 


44  THE   MECHANICAL    FACTORS    OF   DIGESTION 

through  a  local  reflex,  we  must  not  forget  that  the  cardia  is 
nevertheless  under  the  influence  of  extrinsic  nerves,  and  that 
in  abnormal  states  these  nerves  may  cause  the  sphincter  to 
relax,  and  permit  regurgitation  of  food  that  is  acid.  The 
common  regurgitation  of  gases  may  be  due  to  their  effect  in 
keeping  the  acid  contents  away  from  the  stomach  wall  in  the 
region  of  the  cardia.  Then,  as  the  cardia  relaxes  and  permits 
the  regurgitation  of  gas,  acid  fluid  may  also  escape  before  the 
sphincter  again  closes.  All  these  conditions,  however,  cannot 
be  regarded  as  normal.  Normally,  after  we  have  swallowed 
our  food  and  the  automatic  processes  of  the  stomach  have  begun 
to  work  their  changes  in  it.  one  of  the  automatisms — the  acid 
closure  of  the  cardia — has  the  function  of  preventing  a  back- 
ward escape  of  the  gastric  contents  into  the  mouth.  If  in  the 
performance  of  this  important  function  a  slip  occurs,  and  the 
contents  start  to  escape,  the  secondary  peristalsis  of  the  gullet 
is  able,  as  we  have  seen,  to  bring  to  the  cardia  important  aid. 


REFERENCES. 

1  See  His,  Arch.  f.  Anal.,  1903,  p.  347  ;  and  Sinuhuber,  Ztschr.  f.  Idin.  Med., 
1903,  1.,  p.  118. 

2  Magendie,  Precis  Elementaire  de  Physidogie,  Paris,  1817,  ii.,  pp.  77,  78. 
The  original  report  was  made  in  1813. 

3  Mosso,  Untersuch.  z.  NaturL  d.  Mensch.  u.  d.  Thiere,  1876,  xi.,  p.  347. 

4  v.  Mikulicz,  Mitth.  a.  d.  Grenzgeb.  d.  M.  u.  Chir.,  1903,  xii.,  p.  596. 

5  Mcltzer,  Berl.  Bin.  Wchnschr.,  1884,  xxi.,  p.  448. 

6  Kronecker  and  Meltzer,  Arch.  f.  Physid.,  1883,  Suppl..  p.  358. 

7  Meltzer,  Arch.  /.  Physid.,  1883,  p.  215. 

8  v.  Openchowski,  Centralbl.  f.  d.  med.  Wissensch.,  1883,  xxi.,  p.  540. 

9  Langley,  J.  Physid.,  1898,  xxiii.,  p.  407. 

10  Langley,  J.  Physid.,  1901,  xxvii.,  p.  249. 

1  Bernard,  Compt.  rend.  Soc.  de  BioL,  Paris,  1849.  i.,  p.  14. 

12  Schiff,  Lerom  snr  la  Physidogie  de  la  Digest  ion,  Florence  and  Turin,  1867, 
i.,  p.  350  ;  ii.,  p.  377. 

13  Kronecker  and  Meltzer,  Arch.  /.  Physid.,  1883.  Suppl.,  p.  348. 

14  Krehl,  Arch.  j.  Physiol.,  1892,  Suppl.,  p.  286. 

5  Katschkowsky,  Arch.  /.  d.  ges.  Physiol.,  1901,  Ixxxiv.,  pp.  29,  30. 

6  Sinnhuber.  Ztschr.  f.  Idin.  Med.,  1903,  1.,  p.  117. 

17  Starck,  Munchen.  med.  Wchnschr.,  1904,  Ii.,  p.  1514. 

8  v.  Mikulicz,  Mitih.  a.  d.  Grenzgeb.  d.  M.  u.  Chir.,  1903,  xii.,  p.  584. 

9  Kelling,  Arch.  f.  Uin.  Chir.,  1901,  Ixiv.,  p.  403. 

20  Kronecker,   article    "  Deglutition,"  Dictionnaire  de  Physidogie  (Richet), 
Paris,  19CO,  iv.,  p.  744. 

-1  Schiff,  loc.  tit.,  ii.,  p.  333. 

2  Basslinger,  Untersuch.  z.  Saturl.  d.  Mensch.  u.  d.  Thiere,  1860,  vii.,  p.  359 

3  Kronecker  and  Meltzer,  Arch.  /.  Physid.,  1883,  Suppl.,  p.  347. 
!1  Cannon,  Aw.  J.  Physid.,  1903.  viii.,  p.  xxii. 

5  Kelling.  Ztschr.  f.  Bid.,  1903,  xliv.,  p.  234. 

Pawlow,  The  Work  of  the  Digestive  Glands,  London,  1902,  p.  97. 
27  Kast,  Berl.  Uin.  Wchnschr.,  1906,  xliii.,  p.  947. 


CHAPTER  V 

THE  MOVEMENTS  OF  THE  STOMACH 

THE  function  of  the  stomach  as  reservoir,  ready  to  receive 
within  a  short  period  a  generous  provision  of  food,  and  arranged 
to  deliver  this  food  to  the  intestine  during  a  much  longer  period, 
in  proper  amount  and  at  proper  intervals,  has  already  been 
mentioned.  This  reservoir,  however,  is  itself  a  place  of  active 
digestion.  In  it  the  ptyalin  of  saliva  can  continue  to  act  for  an 
hour  or  more,  if  the  amount  of  food  taken  is  large.  And  the 
peptic  digestion  peculiar  to  the  stomach  is  an  important  pre- 
liminary to  the  completion  of  proteolysis  by  the  action  of  trypsin 
and  erepsin  in  the  intestine.  Even  in  vitro  the  course  of  tryptic 
digestion  is  more  rapid  and  more  intense  if  it  has  been  preceded 
by  peptic  digestion  ;l  while  erepsin,  incapable  by  itself  of  attacking 
most  natural  proteins,  must  await  the  changes  wrought  by  the 
other  enzymes  before  it  can  become  effective.  The  sequence  of 
action  of  these  ferments  in  an  order  which  gives  greatest  efficiency 
is  only  one  of  many  instances  of  remarkable  interrelations  in 
the  digestive  canal.2  Besides  being  a  receptacle  for  ingested 
food,  therefore,  the  stomach  is  also  the  seat  of  important  pre- 
paratory stages  of  digestion.  In  promoting  these  digestive 
changes,  the  other  mechanical  activities  of  the  stomach  play  their 
part,  by  churning  together  food  and  secretions.  And  when  this 
process  has  proceeded  to  a  proper  stage,  they  propel  the  altered 
food  onward  for  further  digestion,  as  rapidly  as  the  duodenum 
is  ready  to  receive  it.  The  functions  of  acting  as  reservoir, 
and  of  mixing  and  propelling  the  food,  are  performed  by  different 
parts  of  the  organ. 

The  anatomy  of  the  stomach  with  reference  to  its  varying 
form  has  been  carefully  discussed  by  Cunningham.3  Since  he 
has  considered  the  relation  between  the  structure  of  the  organ 
and  its  physiological  alterations  of  shape,  we  can  safely  follow 

45 


46  THE   MECHANICAL   FACTORS    OF   DIGESTION 

in  the  main  his  description.  Two  portions  are  to  be  distin- 
guished— a  cardiac  and  a  pyloric  portion.  The  demarcation 
between  the  two  appears  on  the  lesser  curvature  as  a  notch  or 
angular  depression — the  "  incisura  angularis." 

The  fundus  is  separated  from  the  rest  of  the  cardiac  portion 
by  an  imaginary  line  passing  around  the  stomach  from  the 
cardiac  orifice  to  the  opposite  point  on  the  greater  curvature. 
In  man  it  is  defined  as  the  part  lying  above  a  horizontal  plane 
passed  through  the  cardia.  That  part  of  the  cardiac  portion 
lying  between  the  fundus  and  the  incisura  angularis  (called 
by  His  the  "  body  "  of  the  stomach4)  has, 
when  full,  a  tapering  shape.  This  shape 
is,  as  we  shall  later  learn,  of  considerable 
significance  for  the  origin  of  gastric  peri- 
stalsis. 

The   pyloric   portion,    to    the    right    of 
the    incisura    angularis,    is    divisible  into 
the    pyloric    vestibule    and    the    pyloric 
canal.     The  canal,  which  in  man  is  about 
7  SCoFEMATHE     3   centimetres   long,   is   a   region  more  or 
STOMACH.  less  tubular  in  form,  but  always  so  con- 

At  C  is  the   cardia ;     tracted  as  to  be  clearly  marked  off  from 

F,  fundus ;  IA,  inci-      ,,  , .,     ,         mi  , .,     «     v       i 

sura   angularis ;    B,     tne  vestibule.     The  vestibule  lies  between 
body  ;    PC,   pyloric     ^ne  incisura  angularis  and  the  pyloric  canal, 

canal  ;  P,  pylorus.  *_J  . 

and  in  the  resting  stomach  is  usually 
pouched  into  the  greater  curvature.  The  term  "  antrum 
pylori,"  meaningless  because  of  its  varied  uses,  we  shall  discard. 
The  wall  of  the  stomach  consists  of  three  coats,  but  our 
interest  centres  on  the  activities  of  the  muscular  coat.  The 
muscles  are  arranged  in  an  outer  longitudinal  layer,  a  middle 
circular  layer,  and  a  set  of  inner  oblique  fibres.  The  longitudinal 
fibres  continue  those  of  the  oesophagus,  and,  radiating  over 
the  cardiac  end,  become  more  marked  along  the  greater  and 
lesser  curvatures  than  on  the  ventral  and  dorsal  surfaces.  Over 
the  pyloric  portion  they  lie  in  a  thick  uniform  layer  terminating 
almost  wholly  at  the  pylorus.  The  circular  fibres,  arranged  in 
rings  at  right  angles  to  the  curved  axis  of  the  stomach,  form 
a  complete  investment.  Toward  the  pyloric  end  they  become 
gradually  more  numerous,  and  around  the  pyloric  canal  they 
form  a  very  well  defined  stratum,  increasing  in  thickness  towards 
the  duodenum,  and  at  the  duodeno-pyloric  junction  forming 


THE   MOVEMENTS    OF   THE   STOMACH  47 

the  strong  pyloric  sphincter.  The  sphincter  is  clearly  separated 
from  the  circular  coat  of  the  duodenum  by  a  distinct  septum  of 
connective  tissue — an  interruption  of  continuity  with  physio- 
logical significance.  At  the  incisura  angularis  is  another  special 
thickening  of  the  circular  fibres,  called  by  early  writers  the 
"  transverse  band."  The  oblique  fibres  start  from  the  left  of 
the  cardia,  and  pass  as  two  strong  bands  along  the  anterior  part 
of  the  dorsal  and  ventral  surfaces,  giving  off  fine  fasciculi  to  the 
circular  layer ;  towards  the  pyloric  portion  they  gradually 
disappear.  It  is  probable  that  these  bands  have  an  interesting 
function  only  recently  suspected. 

In  1898,  Dr.  F.  H.  Williams  and  I  made  observations  on  the 
changes  of  form  of  the  normal  human  stomach  during  digestion.5 
We  found  that  while  early  in  gastric  digestion,  when  the  subject 
was  standing,  the  greater  curvature  might  reach  several  centi- 
metres below  the  umbilicus  (the  pylorus  being  then  considerably 
above  this  level),  in  the  later  stages,  as  the  stomach  shortens, 
the  pylorus  becomes  the  lowest  point.  The  changes  suggested 
that  the  contraction  of  the  longitudinal  and  oblique  fibres  between 
the  two  fixed  points,  cardia  and  pylorus,  resulted  in  a  tendency 
for  the  lumen  to  take  a  more  nearly  straight  course  between  the 
two  orifices.6  X-ray  observations  by  Morton  and  Hertz7  on 
seventeen  healthy  young  men  show  that  in  the  vertical  position 
the  greater  curvature  lies  from  1  to  12  centimetres  below  the 
umbilicus.  Nothing  is  stated  regarding  the  amount  of  gastric 
contents  in  these  cases,  an  important  consideration,  as  we  have 
seen.  After  an  extensive  X-ray  study  of  the  shape  and  position 
of  the  stomach,  Holzknect8  has  declared  that  the  "  normal  " 
human  stomach  is  one  in  which  the  pylorus  is  the  lowest  point. 
The  same  view  was  expressed  by  Pfahler,  who,  after  X-ray  ex- 
amination of  thirty-one  healthy  persons,  declared  that  the 
essential  point  of  the  normal  stomach  is  that  "  the  pylorus  be 
on  a  level  with  the  lower  pole."*  Although  both  Holzknect 
and  Pfahler  admit  that  the  normal  stomach  is  relatively  rare, 
they  support  their  opinion  by  the  argument  that  the  stomach 
is  a  reservoir,  that  a  reservoir  should  always  be  placed  higher 
than  its  outlet,  and  that  therefore  the  "  normal  "  stomach  is 
always  set  above  the  pyloric  outlet  as  its  lowest  point. 

The  view  expressed  by  Holzknect  and  Pfahler  is  in  agreement 
with  an  unfortunate  conception  of  the  emptying  of  the  stomach 
which  has  in  the  past  prevailed  among  some  surgeons,  who  have 


48 


THE    MECHANICAL    FACTORS    OF   DIGESTION 


assumed  that  the  stomach  is  emptied  by  gravity  drainage.  We 
need  not  do  more  than  note  in  passing  that  in  the  obviously 
normal  stomach  of  the  dog  or  cat  the  pylorus  is  nearly  the  highest 
point  when  the  animal  is  in  the  standing  position,  and  that  the 
so-called  "  normal  "  human  stomach  could  remain  satisfactory 
for  gravity  drainage  only  so  long  as  a  person  holds  the  upright 
position  or  lies  on  his  right  side.  A  shift  to  the  left  side  upsets  the 
nice  hydraulic  arrangement,  for  it  places  the  pylorus  at  the  highest 
point  of  the  stomach,  and  then  how  can  the  contents  pass  out  ? 

The  essential  fallacy  in 
the  idea  of  gravity  drain- 
age from  the  stomach  results 
from  a  failure  to  regard 
the  pressure  relations  in <• 
the  abdominal  cavity.  The 
weight  of  the  alimentary 
canal,  as  such,  is  approxi- 
mately that  of  water.  The 
food  swallowed  or  under- 
going gastric  digestion  has. 
approximately  the  weight 
of  water.  The  pressure  in 
any  part  of  the  inactive 
alimentary  canal,  as  Weis- 
ker  proved,10  is  due  to  the 
weight  of  the  overlying  ab- 
dominal organs.  If  the 
canal  is  inactive,  therefore, 
the  food  is  as  if  surrounded 
by  water.  Water  resting  in  water  is,  of  course,  in  exact  equi- 
librium. And  even  when  the  body  is  in  the  upright  position , 
and  a  large  artificial  opening  connects  the  stomach  and 
the  intestine,  water  will  not  run  out :  "  because  of  the  hydro- 
static relations  in  the  abdomen,  gravity  can  have  no  effect."  n 
"  Drainage  "  in  the  common  usage  of  that  term  is  therefore 
impossible.  That  the  food  may  move  onward  through  the 
alimentary  canal,  muscular  contraction  is  necessary  to  create 
a  difference  of  pressure. 

The  muscular  activity  of  the  stomach  is  exhibited  differently 
at  the  two  ends.  Near  the  middle  of  the  body  of  the  stomach 
(at  1  to  6,  Fig.  3)  peristaltic  waves  take  their  origin,  and  course 


FIG.  3. — OUTLINES  OF  AN  ALMOST  IN- 
STANTANEOUS RADIOGRAPH  OF  THE 
STOMACH  (CAT)  DURING  DIGESTION. 

0  =  cardia;  P  =  pylorus.  At  1,  2,  3,  4, 
and  5,  are  indentations  due  to  a  series 
of  constriction  rings  (peristaltic  waves) 
passing  towards  the  pylorus. 


THE   MOVEMENTS    OF  THE   STOMACH 


49 


towards  the  pylorus.  The  region  above  1  to  6  usually  exerts 
merely  a  tonic  grasjLon  its  contents,  and  does  not  display  peri- 
stalsis. By  a  study  of  the  pressure  at  various  parts  of  the 
stomach  in  man,  Moritz12  and  v.  Pfungen13  inferred  that  the 
cardiac  end  of  the  stomach  must  be  quiet,  and  that  the  motor 
functions  were  performed  mainly  by  the  pyloric  end.  The 
same  conclusion  was  earlier  expressed  by  Leven.14  Not  until 
the  X  rays  were  used,  however,  was  the  evidence  of  the  way  in 


FIG.  4. — TRACINGS  OF  THE  SHADOW  CAST  BY  THE  STOMACH  (CAT),  SHOWING 
CHANGES  IN  THE  SHAPE  or  THE  ORGAN  AT  INTERVALS  OF   AN  HOUR 

DURING  THE   DIGESTION    OF   A   MEAL. 


which  the  two  regions  of  the  stomach  perform  their  separable 
functions  clear  and  decisive. 

The  significance  of  these  two  physiologically  distinct  regions 
is  indicated  by  outlines  of  the  shadow  of  the  stomach  made  at 
regular  intervals  during  digestion  (see  Fig.  4).*  Comparison  of 
these  tracings  shows  that  as  digestion  proceeds  the  change  of 
form  in  the  pyloric  portion  is  relatively  slight.  The  first  region 
to  decrease  in  size  is  that  part  of  the  body  of  the  stomach  over 
which  the  waves  are  passing.  As  food  is  discharged  into  the 
intestine,  the  circular  muscle  of  this  middle  region  of  the  stomach 

*  For  a  more  complete  series,  see  Cannon,  Am.  J.  Physiol.,  1898,  i.,  pp.  370- 
372. 


50  THE   MECHANICAL  FACTORS    OF  DIGESTION 

contracts  tonically  until  (Fig.  4,  2  and  3)  a  tube  is  formed,  with  the 
full  cardiac  pouch  at  the  upper  end,  and  the  active  pyloric  portion 
at  the  other.  Along  the  tube  shallow  peristaltic  waves  still 
continue.  Now  the  radiating  fibres  at  the  cardiac  end  begin 
to  squeeze  the  contents  into  the  tubular  portion.  This  process, 
accompanied  by  a  slight  shortening  of  the  tube,  continues  until 
the  shadow  cast  by  the  contents  is  almost  obliterated  (Fig.  4, 
6  and  7).  The  waves  of  constriction  moving  along  the  tubular 
portion  press  the  food  onward  as  fast  as  they  receive  it  from  the 
contracting  cardiac  pouch,  and  when  the  pouch  is  at  last  emptied 
they  sweep  the  contents  of  the  tube  into  the  vestibule.  There  the 
operation  is  continued  by  deeper  constrictions,  till  finally  nothing 
but  a  slight  trace  of  food  in  the  cardiac  end  is  to  be  seen. 

On  the  basis  of  this  description  of  the  changes  in  the  cat's 
stomach,  Cunningham  has  examined  post  mortem  the  form  of 
the  organ  in  man,  and  has  found  not  infrequently  a  similar 
tubular  part  extending  from  the  middle  of  the  body  to  the 
pylorus,  and  distinctly  separable  from  the  saccular  cardiac  end. 
X-ray  observations  in  man  reveal  the  same  conditions.  In 
accordance  with  these  facts,  Cunningham  has  suggested  the 
term  "  cardiac  sac  "  and  "  gastric  tube  "  to  designate  these  two 
portions  of  the  stomach. 

Concerning  the  action  of  the  cardiac  pouch  or  sac,  little  more 
need  be  stated.  Since  it  lies  close  beneath  the  diaphragm,  it  is 
exposed  to  repeated  gentle  pressure  with  each  respiration.  Since 
the  upper  border  of  the  sac  is  moved  more  than  the  lower  border, 
the  contents  must  be  slightly  kneaded  by  the  alternate  contrac- 
tion of  the  diaphragm  and  the  muscles  of  the  abdominal  wall.15 

The  function  of  the  stomach  as  a  reservoir  serving  out  its 
contents  a  little  at  a  time,  so  that  the  intestinal  digestive  pro- 
cesses are  not  overwhelmed  by  the  sudden  arrival  of  a  great  mass 
of  material,  is  at  first  performed  by  the  entire  organ,  but  later  is 
chiefly  performed  by  the  cardiac  sac.  The  advantage  thus 
secured  to  the  intestines  can  be  claimed  also  for  the  stomach 
itself.  For,  as  the  foregoing  description  indicates,  and  as  experi- 
ments to  be  described  later  will  prove,  the  stomach  mixes  its 
secretion  with  the  food  in  the  busy  vestibule  over  which,  through- 
out the  period  of  gastric  digestion,  constriction  waves  are  con- 
tinuously running ;  and  the  cardiac  sac,  an  active  reservoir, 
presses  out  its  contents  little  by  little  as  the  churning  mechanism 
in  the  pyloric  end  is  ready  to  receive  them. 


THE  MOVEMENTS  OF  THE  STOMACH        51 

Concerning  gastric  peristalsis  two  views  have  long  been  held. 
According  to  the  older  view,  which  still  has  its  supporters,16 
the  stomach  is  completely  divided  at  the  transverse  band  by 
each  recurrent  wave,  and  the  vestibule  then  contracts  simul- 
taneously in  all  parts  in  a  systolic  manner.  According  to  the 
newer  view,  developed  by  recent  research,  the  waves  sweep 
from  their  origin  to  the  pylorus,  and  do  not  partition  the  stomach 
into  two  chambers.  Since  the  conception  of  the  course  of  gastric 
peristalsis  affects  in  an  important  way  the  conception  of  its 
functions,  we  may  profitably  consider  the  evidence  presented 
in  support  of  the  two  views. 

Beaumont,  in  his  famous  experiments  on  Alexis  St.  Martin, 
observed  how  a  thermometer  tube  introduced  through  the  fistula 
was  affected  by  the  motions  of  the  stomach,  and  drew  the  follow- 
ing conclusions  :  "  The  circular  or  transverse  muscles  contract 
progressively  from  left  to  right.  When  the  impulse  arrives  at 
the  transverse  band,  this  is  excited  to  more  forcible  contraction, 
and,  closing  upon  the  alimentary  matter  and  fluids  contained  in 
the  pyloric  end,  prevents  their  regurgitation.  The  muscles  of 
the  pyloric  end,  now  contracting  upon  the  contents  contained 
there,  separate  and  expel  some  portion  of  the  chyme."17  In 
close  accord  with  this  description  of  the  movements  of  the  human 
stomach  is  the  account  given  by  Hofmeister  and  Schutz  of  the 
activities  of  the  excised  stomach  of  the  dog.18  The  stomach, 
which  was  placed  in  a  moist  chamber  kept  at  body  temperature, 
remained  active  for  from  sixty  to  ninety  minutes.  A  typical 
movement  of  the  organ  consisted  of  two  phases.  In  the  first 
phase  a  constriction  of  the  circular  fibres  started  a  few  centi- 
metres from  the  cardia,  and  passed  towards  the  pylorus.  As 
the  constriction  proceeded,  it  increased  in  strength  until  a 
maximum  was  reached  about  2  centimetres  in  front  of  the  vesti- 
bule. This  annular  contraction,  called  by  Hofmeister  and 
Schutz  the  "  preantral  constriction,"  closed  the  first  phase. 
Immediately  thereafter  the  strong  transverse  band  contracted 
and  shut  off  the  vestibule  from  the  remainder  of  the  stomach. 
Immediately  a  general  contraction  of  the  muscles  of  the  pyloric 
end  followed.  Kelaxation  began  at  the  transverse  band,  and 
progressed  slowly  towards  the  pylorus.  Moritz,19  who  studied 
gastric  movements  by  introducing  recording  balloons  into  the 
dog  and  man,  and  Ducceschi,20  who  used  the  same  method  in 
the  dog,  found  marked  alterations  of  the  pressure  in  the  pyloric 


52  THE   MECHANICAL   FACTORS    OF  DIGESTION 

end,  which  were  not  transmitted  to  the  cardiac  end.  They 
inferred,  therefore,  that  the  pyloric  end,  separated  from  the 
remainder  of  the  stomach,  had  its  own  distinct  systole  and 
diastole.  By  introducing  the  gastroscope  through  fistulas  in 
dogs  and  men,  Kelling  noted  so  great  a  narrowing  in  the  region 
of  the  transverse  band  that  large  pieces  of  food  (lumps  of  bread) 
were  lying  before  it.21  Inference  as  to  the  functioning  of  the 
transverse  band  was  drawn  by  Schemiakine,  who,  while  watching 
through  a  fistula  at  the  pylorus,  noted  that  the  food  was  not 
continuously  present  there,  but  came  in  separate  allotments.22 
Kaufmann's  experimental  evidence  that  vagus  stimulation  pro- 
duced complete  contraction  of  the  band  may  be  added.23  And 
more  recently  Auer  has  reported  that  in  the  rabbit,  when  ex- 
trinsic nerves  have  been  severed,  gastric  peristalsis  is  empha- 
sized at  the  transverse  band  by  a  deep  constriction,  which 
divides  the  stomach,  and  that  thereupon  the  vestibule  contracts 
as  a  whole  in  a  typical  systole.24 

As  some  of  the  foregoing  evidence  definitely  proves,  the 
circular  muscle  at  the  beginning  of  the  pyloric  portion  is  capable 
of  powerfully  contracting  and  completely  dividing  the  gastric 
lumen.  Indeed,  in  my  first  observations  on  the  stomach  I  saw 
the  organ  thus  divided  after  I  gave  the  animal  apomorphine  or 
mustard  to  induce  vomiting.25  But  what  the  stomach  is  capable 
of  doing  is  not  proof  of  normal  functioning.  Obviously,  in  my 
observations  unnatural  stimulation  was  employed.  Is  not  the 
same  true  also  of  the  other  observations  supporting  the  concep- 
tion of  complete  separation  of  the  cardiac  and  pyloric  portions  ? 
Beaumont  admitted  that  the  thermometer  tube  which  he  used 
was  an  irritant.  "  If  the  bulb  of  the  thermometer,"  he  wrote, 
"  be  suffered  to  be  drawn  down  to  the  pyloric  extremity,  and 
retained  there  for  a  short  time,  or  if  the  experiments  be  repeated 
too  frequently,  it  causes  severe  distress,  and  a  sensation  like 
cramp,  or  spasm,  which  ceases  on  withdrawing  the  tube,  but 
leaves  a  sense  of  soreness  or  tenderness  at  the  pit  of  the  stomach."26 
Perhaps  a  gastroscope  in  the  stomach  might  have  a  similar  effect. 
Even  a  rubber  sound  introduced  into  the  human  stomach 
becomes,  according  to  Moritz,  a  source  of  irritation.27  Of  course, 
inferences  drawn  from  study  of  the  excised  stomach  and  from 
the  movements  of  food  seen  through  a  fistula  must  be  standard- 
ized by  observations  made  under  more  natural  and  more  instruc- 
tive conditions. 


THE   MOVEMENTS    OF  THE   STOMACH  53 

I  have  less  hesitation  in  suggesting  that  complete  division  of 
the  stomach  at  the  transverse  band  is  the  result  of  unnatural 
stimulation  because  of  my  own  experience.  Many  times  I  have 
carefully  watched  with  the  X  rays  gastric  peristalsis  in  human 
beings,  monkeys,  dogs,  cats,  white  rats,  and  guinea-pigs,28  and 
although  the  waves  moving  into  the  pyloric  half  of  the  vesti- 
bule have  at  times  almost  obliterated  the  lumen,  I  have  never 
seen  such  deep  constrictions  at  the  beginning  of  the  pyloric 
portion.  The  systole  of  the  vestibule  in  the  rabbit  I  have  noted 
in  one  instance,  but  I  have  also  watched  in  the  rabbit's  stomach 
continuous  peristalsis,  running  from  the  middle  of  the  organ  to 
the  pylorus,  as  in  the  other  animals,  without  any  obliteration  of 
the  gastric  lumen. 

The  observation  that  peristaltic  waves  run  all  the  way  to 
the  pylorus — first  reported  in  May,  1897 29 — was  immediately 
confirmed  by  the  X-ray  studies  of  Koux  and  Balthazard30  on 
frogs,  dogs,  and  human  beings.  Recently,  with  greatly  improved 
methods,  Kastle,  Bieder,  and  Rosenthal 31  have  obtained  in- 
stantaneous radiographs  of  the  human  stomach,  and  have  com- 
pletely substantiated  our  early  contention  that  the  pyloric  end 
is  normally  not  separated  from  the  rest  of  the  stomach,  and  that 
the  waves  are  continued  over  the  vestibule. 

The  importance  of  a  correct  conception  of  the  movements  of 
the  pyloric  portion  lies  in  its  significance  for  our  understanding 
of  the  functions  of  this  part  of  the  stomach.  If  the  transverse 
band  completely  closes  the  lumen,  and  the  vestibule  then  under- 
goes a  systolic  contraction,  the  function  of  this  portion  must  be 
mainly  one  of  expelling  the  food  into  the  duodenum.*  On  the 
other  hand,  if  the  waves  sweep  without  interruption  over  this 
region,  deepening  as  they  go,  they  may  have  two  functions — 
that  of  expelling  the  food,  if  the  pylorus  opens ;  and  that  of 
^nixing  the  foocl  with  the  gastric  juice,  if  the  pylorus  remains 
closed.  Because  observations  under  normal  conditions  support 
the  latter  conception  of  the  activity  of  the  vestibule,  we  are 
warranted  in  concluding  that  it  has  a  more  important  function 
than  that  of  merely  expelling  gastric  contents  into  the  intestine. 
After  summarizing  the  description  given  by  Hofmeister  and 
Schutz,  Ewald,  for  a  priori  reasons,  declared  :  "  I  cannot  accept 

*  Calculation  shows  that  the  volume  of  the  two  parts  of  the  moderately 
filled  stomach  of  the  dog  is  such  that  if  at  each  "  diastole  "  the  vestibule. were 
filled,  and  at  each  "  systole  "  it  forced  the  contents  into  the  duodenum,  the 
stomach  would  be  emptied  within  two  minutes  1 


54  THE   MECHANICAL   FACTORS    OF  DIGESTION 

this  view.  The  plain  fact  that  the  pyloric  portion  secretes  a 
strongly  digesting  fluid  .  .  .  proves  it  to  be  an  important  part  for 
the  peptonizing  function  of  the  stomach."32  The  account  of 
the  remarkable  manner  in  which  the  pyloric  portion  performs 
this  function  must  be  deferred  until  we  consider  the  effects  of 
gastric  movements  on  the  contained  food. 

When  an  animal  is  examined  with  the  X  rays  immediately 
after  receiving  a  meal  which  fills  the  stomach,  there  appears 
within  a  brief  interval  a  slight  annular  constriction  near  the 
beginning  of  the  vestibule,  which  moves  slowly  to  the  pylorus. 
This  is  followed  by  several  waves  recurring  at  regular  intervals 
in  the  same  region.  Two  or  three  minutes  later  very  slight  con- 
strictions appear  near  the  middle  of  the  body  of  the  stomach, 
and,  pressing  deeper  into  the  greater  curvature,  course  towards 
the  pyloric  end.  Since  the  waves  are  repeated  rhythmically, 
the  circumference  in  which  they  start  must  pulsate.  And  since 
the  time  required  for  the  waves  to  go  from  the  source  to  the  pylorus 
is  longer  than  the  interval  between  pulsations,  several  waves 
are  always  seen  on  the  stomach  at  the  same  time. 

When  a  wave  sweeps  round  the  bend  into  the  vestibule,  the 
indentation  made  by  it  increases.  As  digestion  proceeds,  the 
constrictions  in  the  region  of  the  vestibule  grow  still  stronger, 
and  finally,  when  the  stomach  is  almost  empty,  they  may,  as 
they  come  near  the  pylorus,  completely  divide  the  cavity.  At 
all  times,  in  the  close  neighbourhood  of  the  pyloric  canal,  the 
circular  and  longitudinal  muscles,  both  of  which  are  here  strongly 
developed,  probably  co-operate  to  decrease  simultaneously  in 
all  directions  the  terminal  segment  of  the  stomach.  Certainly 
there  is  a  fairly  quick  change  from  a  rounded,  bulging  mass  of 
food,  in  front  of  the  advancing  ring,  to  a  much  smaller  mass, 
just  before  the  wave  disappears  at  the  pylorus  (compare  2  and  3, 
Fig.  4).33 

Gastric  peristaltic  waves  do  not  pass  on  to  the  duodenum, 
but  stop  at  the  pylorus.  This  separation  of  the  two  regions  is 
probably  to  be  accounted  for  by  the  interruption  in  the  con- 
tinuity of  the  circular  fibres  just  beyond  the  pyloric  sphincter. 

The  rate  of  recurrence  of  the  waves  varies  in  different  animals. 
In  the  cat  it  ranges  from  four  to  six  waves  per  minute  ;  in  the 
dog  the  rate  is  about  four  per  minute  ;  and  in  man  about  three. 
Age  apparently  has  little  influence  on  the  rate.  The  number 
of  waves  per  minute  in  kittens  about  six  weeks  old  was  within 


THE   MOVEMENTS    OF  THE   STOMACH 


55 


the  limits  of  variation  noted  in  adult  animals.  Under  given 
conditions  the  rhythm  is  remarkably  regular.  I  have  many 
times  been  able  to  tell  within  two  or  three  seconds  when  a  minute 
has  elapsed,  simply  by  observing  the  undulations  as  they  passed 
a  selected  point. 

A  slower  recurrence  of  the  gastric  waves  when  fat  was  fed 
than  when  bread-and-milk  mush  was  fed  suggested  that  there 
might  be  characteristic  rates  for  different  foodstuffs.  Ob- 
servations at  different  intervals  after  feeding  different  foods 
gave  the  following  results  :34 


- 

Number  of 
Observations. 

Average  Rate 
per  Minute. 

Most  Frequent 
Rate. 

Extreme 
Variations. 

Fats 
Proteins 
Carbohydrates 

23 
16 
13 

5-0 
5-2 
5-5 

5-2 

5  to  5-4 

5-8 

4     to6 
4-8  „  5-8 
5     „  6 

The  average  rate  of  peristalsis  increases  from  fats  to  proteins 
and  from  proteins  to  carbohydrates,  and  the  rate  most  frequently 
observed  varies  in  the  same  direction ;  but  the  differences  are  so 
slight  and  the  variation  with  any  given  food  so  great  as  to  make 
it  improbable  that  each  foodstuff  produces  a  characteristic  rate. 
As  a  result  of  my  first  observations  on  the  stomach,  I  stated 
that  in  normal  conditions  gastric  peristaltic  waves  are  con- 
tinuously running,  so  long  as  food  remains  in  the  organ.35 
Hundreds  of  observations  made  since  that  time  on  various 
animals — mainly  on  cats,  but  also  on  dogs,  guinea-pigs,  and 
white  rats — as  well  as  records  from  human  beings,36  have  con- 
firmed the  conclusion  that  peristalsis  continues  uninterruptedly 
until  the  stomach  is  swept  clear  of  its  contents.*  The  number 
of  waves  during  a  single  period  of  digestion  is  larger  than  might 
at  first  be  supposed.  In  a  cat  that  finished  eating,  at  10.52  a.m., 
15  grammes  of  bread,  the  waves  were  running  regularly  at 
eleven  o'clock.  The  stomach,  examined  and  found  active  every 
half-hour,  was  not  empty  until  after  six  o'clock.  At  the  average 
rate  for  carbohydrate  food  (5-5  waves  per  minute),  approxi- 
mately 2,300  waves  passed  to  the  pylorus  during  that  single 
digestive  period.  When  proteins  or  fats  are  fed,  the  stomach 
is  emptied  more  slowly  than  when  equal  amounts  of  carbohydrates 
are  fed.37  Although  the  average  rate  of  gastric  peristalsis,  as 

*  The  rabbit  offers  an  exception  to  this  general  statement. 


56  THE  MECHANICAL  FACTORS    OF  DIGESTION 

we  have  seen,  is  slower  for  proteins  and  fats  than  for  carbo- 
hydrates, the  differences  are  so  slight  that  the  slower  rate  does 
not  compensate  for  the  longer  residence  in  the. stomach.  When 
equal  amounts  of  protein,  fat,  or  carbohydrate,  are  fed,  therefore, 
a  much  larger  number  of  peristaltic  waves,  and  consequently 
a  much  greater  expenditure  of  energy  in  the  contraction  of  gastric 
muscle,  is  required  by  the  proteins  and  fats  than  by  the  carbo- 
hydrates, before  the  stomach  is  emptied. 

In  some  animals  I  have  watched,  the  waves  were  repeated 
less  frequently  as  gastric  digestion  proceeded  ;  but  records  made 
at  intervals  during  seven  hours,  after  feeding  different  foods, 
showed  no  constant  direction  of  variation.  No  general  state- 
ment, therefore,  regarding  the  tendency  of  the  waves  to  vary 
in  rate  as  the  stomach  is  being  evacuated,  can  safely  be  ventured. 

The  condition  for  the  appearance  of  gastric  peristalsis  has 
received  relatively  little  attention.  According  to  Edelmann, 
who  studied  the  stomach  by  means  of  a  balloon  introduced  into 
the  organ,  the  movements  are  temporally  related  to  the  secretion 
of  gastric  juice.  Furthermore,  he  states  that  neutralization  or 
dilution  of  the  gastric  juice  results  in  cessation  of  the  movements, 
which  are  restored  only  when  the  contents  become  again  strongly 
acid.38  In  the  experiments  of  Hedblom  and  myself,  the  feeding 
of  acid  food  was  attended  by  especially  deep  and  rapid  peristaltic 
waves ;  the  rate  was  usually  slightly  faster  than  six  waves  per 
minute.39  And  the  feeding  of  fatty  food,  which  inhibits  gastric 
secretion,  was  in  my  experience  usually  attended  by  relatively 
shallow  gastric  waves.40  Although  there  is  this  evidence  of 
concomitant  variation  of  acid  gastric  contents  and  peristalsis, 
it  is  not  proof  that  the  waves  are  the  result  of  an  acid  stimula- 
tion. Indeed,  I  have  observed  deep  and  strong  peristaltic 
waves  in  the  stomach  when  the  contents  were  strongly  alkaline.41 
And,  furthermore,  peristalsis  starts  immediately,  when  food  is 
introduced  into  an  empty  stomach,  if  only  the  organ  is  at  the 
time  in  a  state  of  tonic  contraction.  The  secretion  of  gastric 
juice  does  not  occur  with  such  promptness.  The  causal  relation 
does  not  exist,  I  believe,  between  secretion  and  peristalsis  but 
between  these  two  and  a  common  antecedent  factor.  A  dis- 
cussion of  this  matter  must,  however,  be  deferred  until  later. 

A  modification  of  the  normal  movements  of  the  stomach  is 
seen  when  vomiting  occurs.  Vomiting  can  be  induced  by  irrita- 
tion of  the  gastric  mucosa,  or  by  stimulation  of  centres  in  the 


THE   MOVEMENTS    OF  THE   STOMACH  57 

medulla,  or,  as  Valenti  has  recently  shown,  by  the  excitation 
of  a  well-defined  region  between  the  pharynx  and  the  top  of  the 
•oesophagus.42  The  centrifugal  impulses  pass  through  the  vagi, 
dilating  the  cardia.  These  impulses  also  cause  dilation  of  the 
cardiac  end  of  the  stomach,  while  increasing  the  tonus  of  the 
pyloric  region.  X-ray  observations  on  cats  given  apomorphine 
subcutaneously,  or  mustard  by  stomach-tube,43  correspond 
closely  with  Openchowski's  description  of  the  appearances  of  the 
exposed  stomach  during  emesis.  The  first  change  is  the  total 
inhibition  of  the  cardiac  end  of  the  stomach,  which  becomes  a 
perfectly  flaccid  bag.  This  is  followed,  when  apomorphine  has 
been  given,  by  several  deep  contractions  that  sweep  from  the 
mid-region  of  the  organ  towards  the  pylorus,  each  of  which 
stops  as  a  deep  ring  at  the  beginning  of  the  vestibule,  while  a 
slighter  wave  continues.  Finally,  in  all  cases,  a  strong  con- 
traction at  the  angular  incisure  completely  divides  the  gastric 
cavity  into  two  parts.  Although  waves  continue  running 
over  the  vestibule,  the  body  of  the  stomach  and  the  cardiac 
sac  are  fully  relaxed.  Now  a  simultaneous  jerk  of  the 
diaphragm  and  the  muscjes_of  the  abdominal  wall  shoots  the 
contents  out  through  the  relaxed  cardia.  As  these  jerks  are 
repeated,  the  gastric  wall  seems  to  tighten  around  the  remnant 
of  contents.  Once  during  emesis  I  saw  an  antiperistaltic  con- 
striction start  at  the  pylorus  and  run  back  over  the  vestibule, 
completely  obliterating  the  cavity,  but  stopping  at  the  angular 
incisure.  In  the  process  of  ridding  the  gastric  mucosa  of  irri- 
tants, therefore,  the  stomach  plays  a  relatively  passive  role. 


REFERENCES. 

1  Fischer  and  Abderhalden,  Ztschr.  f.  physiol.  Chem.,  1903,  xl.,  p.  216. 

2  See    Cannon,   "  The    Correlation    of  the  Digestive   Functions,"   Boston 
M.  and  8.  J.,  1910,  clxii.,  p.  97. 

3  Cunningham,  Tr.  Roy.  Soc.,  Edinb.,  1906,  xlv.,  p.  9. 

4  His,  Arch.  f.  Anat.,  1903,  p.  350. 

5  See  Williams,  The  Rontgen  Rays  in  Medicine  and  Surgery,  New  York,  1901, 
pp.  360,  365,  370. 

6  Cf.  His,  loc.  cit.,  p.  362,  Figs.  1  to  4  ;  and  Bettmann,  Phila.  Month.  M.  J., 
1899,  i.,  p.  133. 

7  See  Hertz,  Quart.  J.  Med.,  1910,  iii.,  p.  375. 

8  Holzknecht,  Berlin,  klin.  Wchnschr.,  1906,  xliii.,  p.  128. 

9  Pfahler,  J.  Am.  M.  Ass.,  1907,  xlix.,  p.  2069. 

10  Schmidt's  Jahrb.,  Leipz.,  1888,  ccxix.,  p.  284. 

11  Kelling,  Arch.  f.  d.  Verdauungskr.,  1900,  vi.,  pp.  445,  456. 

12  Moritz,  Ztschr.  f.  Bid.,  1895,  xxxii.,  p.  359. 

13  v.  Pfungen,  Centralbl.  f.  Physiol.,  1887,  i.,  p.  220. 

14  Leven,  Traite  des  Maladies  de  VEstomac,  Paris,  1879,  p.  16. 


58  THE   MECHANICAL   FACTORS    OF  DIGESTION 

15  See  Cannon,  loc.  cit.,  p.  373. 

16  See  Boldireff,  Internat.  Beitr.  z.  Path.  u.  Therap.  d.  Ernahrungsstor.,  1910, 
i.,p.  14. 

17  Beaumont,  Physiology  of  Digestion,  Plattsburgh,  1833,  p.  115. 

18  Hofmeister  and  Schutz,  Arch.  f.  exper.  Path.  u.  Pharmakol.,  1885,  xx.,  p.  7. 

19  Moritz,  loc.  cit.,  p.  362. 

20  Ducceschi,  Arch,  per  la  Sc.  Med.,  1897,  xxi.,  p.  134. 

21  Kelling,  Arch.  f.  Ttlin.  Chir.,  1900,  Ixii.,  p.  22. 

22  Schemiakine,  Arch,  des  Sc.  Biol.,  St.  Petersb.,  1904,  x.,  p.  170. 

23  Kaufmann,  Wien.  med.  Wchnschr.,  1905,  lv.,  p.  1582. 

24  Auer,  Am.  J.  PhysioL,  1908,  xxiii.,  p.  170. 

25  Cannon,  Am.  J.  PhysioL,  1898,  i.,  p.  374. 

26  Beaumont,  loc.  cit.,  p.  114. 

27  Moritz,  loc.  cit.,  p.  369. 

28  See  Cannon,  Am.  J.  PhysioL,  1898,  i.,  p.  367  ;  1902,  viii.,  p.  xxii. 

29  Cannon,  Science,  June  11,  1897,  p.  902. 

30  Pvoux  and  Balthazard,  Compt.  rend.  Soc.  de  Biol.,  Paris,  June,  1897,  xlix., 
pp.  704,  785  ;  and  Arch,  de  PhysioL,  1898,  xxx.,  p.  90. 

31  Kastle,  Rieder,  and    Rosenthal,   Miinchen.  med.    Wchnschr.,  1909,   Ivi., 
p.  281  ;  also  Arch.  Rontgen  Ray,  1910,  xv.,  p.  3. 

32  Ewald,  Lectures  on  Digestion,  London,  1891,  p.  67. 

33  See  Hertz,  loc.  cit.,  p.  381. 

34  Cannon,  Am.  J.  PhysioL,  1904,  xii.,  p.  392. 

35  Cannon,  Am.  J.  Physiol.,  1898,  i.,  p.  367. 

36  Cannon,  Am.  J.  PhysioL,  1903,  viii.,  p.  xxii ;  1905,  xiv.,  p.  344. 

37  Cannon,  Am.  J.  Physiol.,  1904,  xii.,  p.  393. 

38  Edelmann,  Dissertation  (Russian)  abstracted  in  Jahresb.  u.  d.  Fortschr.  d. 
Physiol.,  1906,  xv.,  p.  119. 

39  Hedbiom  and  Cannon,  Am.  J.  Med.  Sc.,  1909,  cxxxviii.,  p.  518. 

40  Cannon,  Am.  J.  Physiol.,  1907,  xx.,  p.  315. 

41  Cannon,  Am.  J.  PhysioL,  1907,  xx.,  pp.  298,  299. 

42  Valenti,  Arch.  f.  exper.  PathoL  u.  Pharmakol.,  1910,  Ixiii.,  p.  136. 

43  Cannon,  Am.  J.  Physiol.,  1898,  i.,  p.  373. 


CHAPTER  VI 

THE  EFFECTS  OF  STOMACH  MOVEMENTS  ON  THE  CONTENTS 

WHATEVER  the  amount  of  food  sent  to  the  stomach,  the  organ 
has  a  wonderful  ability  to  adapt  itself  with  precision  to  the 
volume  of  the  contents.  Even  during  the  short  time  of  a  single 
digestive  period  the  body  of  the  stomach  may  contract  from 
a  large  conical  sac,  many  centimetres  in  circumference,  to  a 
narrow  tube  little  larger  than  a  loop  of  intestine.  Furthermore, 
during  this  alteration  in  size  the  pressure  remains  practically 
uniform.  The  change  in  the  opposite  direction,  from  smaller 
to  larger  capacity,  Kelling1  proved  could  occur  within  a  minute 
or  two  without  noteworthy  increase  of  intragastric  pressure. 
Thus,  when  he  introduced  into  the  stomach  of  a  dog  240  c.c. 
of  material,  the  pressure  was  7-6  centimetres  of  water  ;  and  when 
this  amount  was  increased  to  460  c.c.,  the  pressure  was  only 
7  centimetres.  Since  he  failed  to  find  persistence  of  pressure 
regulation  in  deep  anaesthesia,  Kelling  inferred  that  it  was  a 
reflex  adaptation.  More  recently,  Sick  and  Tedesko2  have 
proved,  however,  that  the  excised  stomach,  kept  alive  in  warm 
oxygenated  Ringer's  solution,  is  able  to  adapt  itself  to  increase 
of  volume  by  an  intrinsic  relaxation,  especially  in  the  cardiac 
end,  so  that  there  is  no  marked  increase  of  pressure.  Observa- 
tions which  I  have  made  on  cats  entirely  confirm  the  results  of 
both  Kelling  and  Sick  ;  and  I  have  also  seen  the  excised  stomach 
gradually  contract,  as  the  contents  were  decreased,  and  main- 
tain continuously  the  pressure  that  existed  before  the  decrease. 
The  mechanism  by  which  the  stomach  becomes  so  remarkably 
adjusted  to  its  contained  volume  may  exist,  therefore,  within 
itself. 

The  nature  of  the  adjustment  in  the  stomach  wall  is  not  yet 
clearly  explained.  Mere  relaxation  of  the  tonic  contraction  of 
the  gastric  muscle,  according  to  Griitzner,  would  not  account 

59 


60  THE   MECHANICAL   FACTORS    OF   DIGESTION 

for  the  great  changes  in  the  capacity  of  the  stomach  without 
attendant  alterations  of  intragastric  pressure.3  Miiller,4  working 
under  Griitzner's  direction,  compared  the  relaxed  muscle  fibres 
in  the  full  stomach  and  the  contracted  fibres  in  the  empty 
stomach  of  the  frog  and  salamander.  He  found  that,  whereas 
the  length  of  the  relaxed  fibres  was  not  more  than  three  times 
that  of  the  contracted,  the  circumference  of  the  full  stomach 
was  five  times  that  of  the  empty.  The  discrepancy  he  explained 
as  due  to  a  rearrangement  of  the  fibres  :  the  musculature  of  the 
full  stomach  was  composed  of  only  two  or  three  layers  of  fibres, 
while  the  contracted  stomach  had  from  fifteen  to  twenty  layers. 
How  the  fibres  can  thus  slip  by  one  another  and  still  maintain 
continuous  pressure,  and  how,  once  dissociated,  they  are  restored 
to  the  multiplex  composition  of  the  contracted  state  is  not 
explained. 

Another  adjustment  required  by  the  filling  of  the  stomach  is 
that  of  the  abdominal  muscles  to  the  enlargement  of  the  ab- 
dominal contents.  According  to  Kelling,  the  abdominal  contents 
of  the  dog  may  be  increased  100  per  cent,  by  a  single  meal. 
Obviously,  if  the  muscles  of  the  abdominal  wall  do  not  relax, 
intra-abdominal  pressure  must  increase — a  result  which  might 
produce  serious  circulatory  disturbances.  As  the  stomach  is 
filled,  however,  the  muscles  are  relaxed,  and  in  consequence  the 
pressure  within  the  abdomen  is  not  affected  by  taking  food. 
Apparently  this  adaptation  of  the  abdominal  muscles  is  a  reflex 
originated  in  the  stomach  or  intestines ;  for  when  air  or  salt 
solution  is  injected  into  the  peritoneal  cavity,  the  pressure  is  at 
once  increased.5 

The  figures  given  for  intragastric  pressure  vary  somewhat 
with  different  observers,  and,  as  might  be  expected,  the  pressures 
are  different  in  the  less  active  cardiac  end,  holding  the  food  in 
tonic  grasp,  and  in  the  more  active  pyloric  end,  undergoing 
repeated  compression  by  peristaltic  waves.  We  have  already 
learned  that  these  waves,  as  they  move  along  the  pyloric  vestibule, 
press  gradually  deeper  into  the  contents.  The  pressure,  there- 
fore, should  be  greater  at  the  pylorus  than  elsewhere  in  the 
stomach.  Actual  measurement  of  the  pressure  in  the  cardiac  and 
pyloric  ends  of  the  human  stomach  have  been  made.  Von  Pfungen 
introduced  into  the  stomach  of  a  boy  who  had  a  gastric  fistula 
8  centimetres  to  the  left  of  the  mid-line  a  rubber  balloon,  and 
found  that  intragastric  pressure  near  the  fistula  was  upward  from 


THE   EFFECTS    OF  STOMACH   MOVEMENTS  61 

19  centimetres  of  water,  whereas  directly  in  front  of  the  pylorus 
the  pressure  was  162  centimetres  of  water.6  By  means  of  an 
intragastric  bag  passed  down  the  oesophagus,  Moritz  studied  the 
pressures  in  the  two  ends  of  the  stomach  in  a  normal  individual. 
Although  his  figures  are  lower  than  v.  Pfungen's,  they  show 
a  similar  difference  between  the  cardiac  and  pyloric  portions. 
The  usual  pressure  in  the  cardiac  end  varied  between  6  and 
8  centimetres  of  water,  while  in  the  pyloric  end  there  were 
rhythmic  recurrences  of  pressure  amounting  in  some  instances 
to  38,  40,  and  even  60  centimetres  of  water,  though  as  a  rule 
ranging  from  20  to  30  centimetres.7  The  results  obtained  by 
Sick,  who  used  the  method  of  Moritz,  were  confirmatory — 
7  to  16  centimetres  pressure  in  the  cardiac  end,  contrasted  with 
25  to  42  centimetres  in  the  pyloric  end.8 

The  methods  used  in  these  experiments  are  not  above  criticism. 
The  presence  of  the  experimenter's  tube,  especially  in  the  pyloric 
vestibule,  where  deepening  peristaltic  constrictions  narrow  the 
lumen,  may  have  prevented  to  some  extent  a  free  movement  of 
the  contents,  and  may  have  thus  unnaturally  increased  the 
pressure  in  that  region.  Also  the  balloon  may  have  stimulated 
unusually  strong  contractions  in  the  pyloric  portion,  and  in 
that  way  increased  the  difference  between  the  pressures  in  the 
two  ends  of  the  stomach.  Yet  the  results  obtained  are  what 
might  be  expected  from  greater  depth  of  the  constrictions  as 
they  approach  the  pylorus,  and  this  concurrent  evidence  dis- 
tinctly indicates  that  towards  the  pyloric  exit  the  intragastric 
pressure  becomes  considerably  greater  than  it  is  near  the  less 
active  fundus.  This  conclusion  is  confirmed  by  the  manner  in 
which  chyme  is  discharged  into  the  duodenum.  In  my  X-ray 
observations,  whenever  the  chyme  was  permitted  to  emerge, 
I  saw  it  spurted  through  the  pylorus  and  shot  along  the  intestine 
for  several  centimetres.  The  same  testimony  to  the  efficacy  of 
pressure  at  the  pylorus  is  given  by  investigators  who  have 
watched  the  gastric  discharge  through  a  duodenal  fistula. 

The  absence  of  peristalsis  over  the  cardiac  sac,  and  the  presence 
of  gradually  deepening  peristaltic  constrictions  in  the  pyloric 
vestibule,  have  important  practical  consequences.  Before  con- 
sidering them,  however,  we  shall  review  what  is  known  of  the 

O  '  ' 

effects  of  gastric  movements  on  the  contents  of  these  two  parts 
of  the  stomach. 
A  difference  in  the  activities  of  the  two  ends  of  the  stomach 


62  THE   MECHANICAL   FACTORS    OF  DIGESTION 

might  have  been  inferred  from  old  observations  on  the  appear- 
ance of  the  food  in  the  cardiac  and  pyloric  portions.  In  1814, 
Home  described  two  parts  of  the  stomach  of  the  dog,  "  that 
next  the  cardia  the  largest,  and  usually  containing  a  quantity 
of  liquid  in  which  there  was  solid  food,  but  the  other,  which 
extended  to  the  pylorus,  being  filled  entirely  with  half-digested 
food  of  a  uniform  consistence."9  Twenty  years  later  Eberle 
reported  that,  when  the  stomach  of  a  dog  is  carefully  opened 
during  digestion,  the  surface  of  the  mass  in  the  cardiac  end  shows 
signs  of  digestion,  but  the  interior  of  the  mass  remains  unchanged, 
whereas  the  contents  of  the  pyloric  end  are  throughout  uniformly 
mushy  and  fluid.10  Many  years  later,  Ellenberger  and  his 
students  demonstrated  that,  for  several  hours  after  eating,  the 
digestive  processes  in  the  two  ends  of  the  stomach  of  the  horse 
and  the  pig  were  quite  different,  and  that  different  foods  fed 
successively  were  found,  not  uniformly  mixed,  but  arranged 
in  strata.11 

These  excellent  observations  were  for  a  long  time  obscured 
by  Beaumont's  description  of  the  circulation  of  the  food  in  the 
human  stomach,  a  description  so  circumstantial  and  detailed 
as  to  present  all  the  semblance  of  exactness.  "  The  bolus  as  it 
enters  the  cardia,"  Beaumont  wrote,  "  turns  to  the  left ;  passes 
the  aperture ;  descends  into  the  splenic  extremity ;  and  follows 
the  great  curvature  towards  the  pyloric  end.  It  then  returns, 
in  the  course  of  the  small  curvature,  makes  its  appearance  again 
at  the  aperture,  in  its  descent  into  the  great  curvature,  to  perform 
similar  revolutions."12  That  Beaumont's  conclusions  were  based 
on  the  movements  of  a  thermometer  tube  introduced  through 
a  fistula,  and  on  the  appearance  of  particles  of  food  in  the  gastric 
contents  as  they  passed  the  fistulous  opening,  was  not  criticized. 
Yet,  as  we  now  know,  the  irritation  by  the  thermometer  tube 
produced  abnormal  contractions,  and  the  course  which  the  par- 
ticles took  when  out  of  the  observer's  sight  could  not  be  fairly 
judged. 

It  is  easily  possible  to  test  experimentally  the  validity  of 
Beaumont's  inferences  by  watching  with  the  X  rays  the  move- 
ments of  pieces  of  food  prepared  to  throw  a  black  shadow  in  a 
dimly  outlined  stomach.  For  this  purpose  I  made  little  paste 
pellets  of  bismuth  subnitrate,  with  starch  enough  to  preserve 
the  form,  and  gave  them  with  the  customary  food,  containing 
relatively  much  less  of  the  bismuth  salt.  These  pellets,  when 


THE  EFFECTS    OF  STOMACH  MOVEMENTS  63 

partly  dried,  did  not  disintegrate  in  the  stomach  during  the 
gastric  digestion  of  soft  bread.  Several  times  I  was  fortunate 
in  finding  two  of  the  little  balls  in  the  axis  of  the  body  of  the 
stomach,  and  about  a  centimetre  apart.  As  a  constriction  wave 
approached  them,  both  moved  forward,  but  not  so  rapidly  as  the 
wave.  Now,  when  the  constriction  overtook  the  first  ball,  the 
ball  moved  back  towards  the  fundus  through  the  moving  con- 
stricted ring,  in  the  direction  of  least  resistance.  The  wave  then 
overtook  the  second  ball,  and  it  also  passed  backward  to  join  its 
fellow.  At  the  approach  of  the  next  wave  they  were  both  pushed 
forward  once  more,  only  to  be  again  forced  backward,  one  at 
a  time,  through  the  narrow  orifice.  But  as  the  waves  recurred 
in  their  persistent  rhythm,  the  balls  were  seen  to  be  making 
progress — an  oscillating  progress — towards  the  pylorus  ;  for 
they  went  forward  each  time  a  little  farther  than  they  retreated. 
This  to-and-fro  movement  of  the  pellets  was  in  no  way  inter- 
rupted in  the  region  of  the  transverse  band,  which  is  additiona 
good  evidence  that  normally  it  does  not  divide  the  stomach  into 
two  parts.  In  the  pyloric  vestibule,  where  the  peristaltic  waves 
were  deep,  the  oscillations  were  more  marked  than  in  the  body 
of  the  stomach.  On  different  occasions  from  nine  to  twelve 
minutes  elapsed  while  the  balls  were  being  pushed  from  where 
the  waves  first  affected  them  to  the  pylorus  ;  on  the  way,  there- 
fore, they  must  have  been  churned  back  and  forth  by  approxi- 
mately a  half -hundred  constrictions.13 

In  the  cardiac  sac  no  signs  of  currents  were  visible.  Balls 
which  lay  in  this  region  immediately  after  the  food  was  ingested 
kept  their  relative  positions  until  the  sac  began  to  contract,  and 
then  moved  slowly  towards  the  pyloric  end.  The  immobility 
of  the  food  in  the  cardiac  sac  was  also  proved  by  feeding  first 
5  grammes  of  bread  and  bismuth  subnitrate,  then  5  grammes  of 
bread  alone,  and  finally  5  grammes  of  bread  with  the  bismuth 
salt  again.  The  first  stratum  lay  along  the  greater  curvature 
and  extended  into  the  pyloric  vestibule,  the  third  stratum  spread 
along  the  lesser  curvature,  and  the  second  rested  between. 
Tracings  of  this  stratification  of  the  contents  were  made  on  trans- 
parent paper.  Ten  minutes  after  peristalsis  began,  the  strati- 
fication had  entirely  disappeared  towards  the  pyloric  end  of  the 
stomach,  but  in  the  cardiac  end,  after  an  hour  and  twenty 
minutes,  the  layers  were  still  clearly  visible.14 

These  X-ray  observations  on  the  stratification  of  the  gastric 


64  THE   MECHANICAL  FACTORS    OF   DIGESTION 

contents  are  in  fair  agreement  with  the  observations  of  Ellen- 
berger  and  Goldschmidt  on  the  horse,  which  have  since^been 
confirmed  by  Scheunert.15  They  do  not  present  the  arrangement 
so  uniformly  simple  as  Griitzner  has  described  it.16  He  fed  in 
succession  foods  differently  coloured,  and,  after  digestion  had 
continued  for  an  hour  or  more,  killed  the  animal,  froze  the  stomach 
with  its  contents,  and  then  made  sections  of  it.  Frogs  and  toads, 
rats,  cats,  and  dogs,  served  as  subjects  for  the  investigation. 
As  in  the  X-ray  experiments,  he  reports  that  the  first  food  was 
pushed  along  the  greater  curvature  by  the  later  masses,  but  it 
was  also  spread  outwards  from  the  greater  curvature,  in  the  form 
of  a  thin  layer,  which  prevented  the  later  masses,  lying  within, 
from  coming  into  direct  contact  with  the  secreting  mucosa. 
Thus,  whenever  new  food  was  given,  it  nested  in  the  midst  of 
the  food  already  present,  just  as  described  by  Eberle  in  1834. 
In  the  pyloric  end,  Griitzner  found  that  after  digestion  began  the 
strata  soon  became  broken  and  warped. 

Direct  study  of  the  motions  of  the  food  in  the  stomach,  there- 
fore, wholly  discredits  the  account  given  by  Beaumont ;  not 
even  when  the  contents  are  fluid  does  circulation  occur.  On 
the  other  hand,  the  motions  observed  offer  a  complete  explana- 
tion of  the  difference  in  the  gastric  contents  at  the  two  ends  of 
the  stomach  as  described  by  Home  and  Eberle.  Anyone  can 
readily  verify  the  basic  observation  which  first  indicated  the 
separate  functions  of  the  cardiac  and  pyloric  ends.  The  food 
in  the  centre  of  the  cardiac  sac  has  the  same  appearance  after 
an  hour  and  a  half  of  gastric  peristalsis  that  it  had  when  ingest ed,. 
but  the  contents  of  the  pyloric  vestibule,  which  the  waves  have 
been  churning,  are  changed  to  the  consistency  of  thick  soup. 

The  absence  of  any  motions  in  the  contents  of  the  cardiac 
sac  suggested  that  the  food  during  its  stay  there  has  little  oppor- 
tunity to  become  mixed  with  the  gastric  juice,  and  thus  to  undergo 
peptic  digestion.  The  truth  of  this  supposition  was  easily 
proved  experimentally  by  feeding  a  slightly  alkaline  food,  and 
later  testing  the  reaction  of  the  contents  in  various  parts  of  the 
stomach. 

A  cat  which  had  been  without  food  for  fifteen  hours  was  given 
18  grammes  of  mushy  bread  made  slightly  alkaline  with  sodium 
carbonate.  One  hour  and  a  half  after  the  cat  had  finished  eating 
she  was  killed,  and  the  stomach  exposed  by  opening  the  abdomen. 
A  very  small  hole  was  then  made  in  the  wall  of  the  cardiac  sacr 


THE   EFFECTS    OF   STOMACH  MOVEMENTS  65 

and  another  similar  hole  was  made  in  the  pyloric  vestibule. 
By  means  of  a  glass  pipette  food  was  extracted  first  from  the 
periphery  of  the  cardiac  sac  ;  this  food  was  slightly  acid.  The 
cleaned  pipette  was  then  introduced  2*5  centimetres  into  the 
contents  of  the  sac ;  the  food  thus  extracted  gave  the  original 
alkaline  reaction.  Specimens  of  the  fluid  contents  near  the 
pyloric  end,  taken  from  various  depths,  were  all  strongly  acid.17 

These  observations  on  the  cat  I  repeated  on  the  dog.  They 
have  been  completely  confirmed  by  Heyde  working  with  Griitzner. 
Rats,  rabbits,  guinea-pigs,  and  cats,  were  fed  by  Heyde  with 
different  kinds  of  food  mixed  with  acid  indicators,  and  were 
killed  at  different  intervals  after  eating.  The  stomachs  were 
carefully  removed  and  frozen  ;  sections  were  made  through  the 
frozen  contents,  and  the  altered  colour  of  the  indicators  revealed 
at  once  the  extent  of  acidification.  The  inner  layers  of  the 
food  in  the  cardiac  end  retained  for  hours  a  neutral  or  weakly 
alkaline  reaction  ;  only  the  outer  layers  were  slightly  acidified 
and  digested.18 

As  we  have  already  learned,  the  functional  difference  between 
the  cardiac  and  pyloric  ends  of  the  stomach  is  the  same  in  man 
as  in  the  dog,  the  cat,  and  other  experimental  animals.  Does 
a  corresponding  difference  prevail  between  the  character  of  the 
contents  in  the  two  ends  of  the  human  stomach  ?  Does  the 
mass  of  food  in  the  quiet  cardiac  sac  remain  long  unmixed  with 
gastric  juice  while  that  in  the  pyloric  end  is  intimately  churned 
by  the  peristaltic  waves  ?  These  questions  have  been  considered 
by  Sick,19  who,  using  a  specially-devised  stomach-tube,  removed 
samples  of  the  contents  from  the  cardiac  or  pyloric  end  at  will. 
The  subjects  took  a  semi-fluid  test-meal,  and  then  swallowed 
a  cachet  containing  carmine  or  charcoal.  After  a  given  time  the 
stomach-tube  was  introduced,  first  into  the  pyloric,  and  later 
into  the  cardiac  end.  In  spite  of  the  semi-fluid  gastric  contents, 
and  in  spite  of  exercise  by  the  subjects  during  the  interval  of 
digestion,  the  pyloric  part  of  the  stomach  remained  wholly  free 
from  the  colouring  material  for  fifteen  or  twenty  minutes — indeed, 
in  some  cases  for  almost  twenty-five  minutes — while  the  cachet 
had  meanwhile  dissolved  and  liberated  its  contents  into  the  food 
of  the  cardiac  end.  Gradually,  after  thirty  or  forty  minutes, 
the  carmine  powder  appeared  near  the  pylorus.  Sick  also  found 
a  difference  in  the  consistency  of  the  contents  in  the  two  portions 
of  the  stomach  :  in  the  pyloric  end  a  thin  fluid  was  present, 

5 


66  THE   MECHANICAL   FACTORS    OF   DIGESTION 

homogeneous  in  character ;  in  the  cardiac  end  a  lumpy,  rather 
coherent  mass.  He  concluded,  therefore,  that  in  the  human 
stomach,  even  when  the  food  is  somewhat  fluid,  an  important 
difference  exists  between  the  physical  and  chemical  nature  of  the 
contents  of  the  two  ends,  and  that  only  slowly  does  a  com- 
plete mixture  take  place.  This  conclusion  is  supported  by  the 
experiments  of  Prym,20  who  has  furthermore  emphasized  the 
significance  of  this  differential  treatment  of  the  food  for  the 
clinical  examination  of  gastric  contents.  Evidently,  if  the  con- 
tents are  not  a  uniform  and  homogeneous  mixture,  not  only 
may  the  stomach-tube  give  wrong  testimony  regarding  the 
conditions  in  the  organ,  but  the  food  even  when  expressed  as  a 
whole  may  be  equally  deceptive. 

The  application  to  man  of  the  facts  determined  for  animals 
has  been  criticized  by  Hertz,  who  has  declared  that  gas  in  the 
fundus  of  the  human  stomach  (gas  is  practically  always  present) 
causes  the  oesophagus  to  discharge  new  food  either  on  or  slightly 
below  the  upper  surface  of  the  stomach  contents,  and  thus  not 
into  the  centre  of  the  mass  in  the  cardiac  sac.  He  has  also 
suggested  that  the  delay  in  the  appearance  of  the  colouring 
materials  (carmine  and  charcoal)  in  the  pyloric  end,  noted  by 
Sick,  was  due  to  their  first  floating  on  the  surface  of  the  contents, 
whence  they  could  become  only  gradually  incorporated.21  Of 
course  the  question  of  the  stratification  of  the  food  is  really 
not  involved  in  a  consideration  of  the  mechanical  effects  of 
peristalsis  in  one  end  of  the  stomach,  and  mere  tonic  contraction 
in  the  other  end.  Hertz  seems  not  to  have  given  due  weight 
to  the  statement  of  Sick  that  about  three-fourths  of  his  subjects 
were  reclining  on  the  right  side,  nor  has  he  offered  any  explana- 
tion of  the  difference  in  the  consistency  of  the  food  from  the 
two  parts  of  the  stomach,  which  Sick  reported.  Certainly  the 
greater  size  of  the  human  stomach  does  not  cause  it  to  act  differ- 
ently on  the  food  than  do  the  stomachs  of  dogs  and  cats,  for, 
as  already  stated,  Ellenberger  and  Goldschmidt  proved  that 
there  was  no  general  mixture  of  the  gastric  contents  in  the  horse 
during  several  hours  after  the  ingestion  of  food.  The  main  argu- 
ment of  Hertz  seems  to  be  based  on  the  assumption  that  gastric 
contents  are  so  fluid  as  to  be  the  medium  of  rapid  diffusion. 
Experiments  to  be  described  later  show  that  diffusion  does 
indeed  occur  even  in  viscous  gastric  contents,  and  that  when 
the  contents  are  of  a  thin,  fluid  consistency  the  diffusion  may 


THE   EFFECTS    OF  STOMACH  MOVEMENTS  67 

be  rapid.  After  an  ordinary  generous  meal,  however,  with  a 
satisfactory  variety  of  food,  the  gastric  contents,  as  the  autopsy- 
room  demonstrates,  may  not  be  fluid,  but  a  thick  and  mushy 
mass.  In  such  a  mass  diffusion  currents  must  be  slow.  Indeed, 
the  currents  described  by  Beaumont,  resulting  from  the  move- 
ments of  the  gastric  wall,  could  hardly  occur.  Under  such 
circumstances,  therefore,  the  evidence  points  to  the  same  effects 
on  the  food  in  the  two  ends  of  the  human  stomach  as  are  found 
in  animals. 

The  supposed  value  of  the  circulation  of  the  food  in  currents 
running  throughout  the  stomach,  as  described  by  Beaumont, 
lay  in  the  means  it  offered  for  bringing  the  contents  of  the 
stomach  near  to  the  secreting  gastric  mucosa,  and  thus  per- 
mitting the  gastric  juice  to  exert  more  readily  its  action. 
Although  my  X-ray  observations  did  not  support  Beaumont's 
description  of  a  mixing  current  moving  along  the  greater  and 
lesser  curvatures,  they  nevertheless  showed  that  in  the  pyloric 
vestibule  and  the  region  just  before  it  an  admirable  mechanism 
exists  for  bringing  all  of  the  food  into  intimate  contact  with  the 
mucosa  in  that  region.  Evidently,  when  a  constriction  occurs, 
the  mucous  surface  enclosed  by  the  ring  is  brought  close  around 
a  narrow  isthmus  of  food  or  chyme  lying  in  the  axis  of  the  stomach. 
Now,  as  this  constriction  passes  on,  fresh  areas  of  the  mucosa 
are  continuously  pressed  inward  to  form  the  little  orifice.  And 
at  the  same  time,  as  the  constriction  moves,  a  thin  stream  of 
the  gastric  contents  is  continuously  forced  back  through  the 
orifice.  The  result  of  this  admirable  mechanism,  indicated  by 
the  oscillating  pellets,  is  that  every  part  of  the  mucosa  of  the 
pyloric  portion  is  brought  near  to  every  bit  of  food  a  large  number 
of  times  before  the  food  leaves  the  stomach. 

It  is  well  known  that  the  mucosa  of  the  pyloric  portion  of  the 
stomach  does  not  secrete  hydrochloric  acid,  although  it  does 
secrete  pepsin.  Yet  the  contents  of  this  region,  all  observers 
agree,  become  uniformly  acid  in  reaction  soon  after  gastric 
digestion  begins,  and  remain  thus  until  the  stomach  is  emptied. 
We  must  assume,  therefore,  that  the  acid-pepsin  secretion  is 
pressed  onward  from  the  surface  of  the  contents  of  the  cardiac 
portion,  by  the  gentle  waves  of  peristalsis  in  that  region,  and 
gradually  mixed  into  the  contents  of  the  vestibule.  Meanwhile, 
however,  the  deep  waves  approaching  the  pylorus  have  churned 
the  vestibular  food  with  the  local  pepsin  secretion,  and  now, 


68  THE   MECHANICAL   FACTORS    OF  DIGESTION 

as  the  imported  acid  appears,  proteolytic  digestion  can  progress 
rapidly.22  Thorough  mixture  of  the  food  with  the  secretion  of 
the  vestibule  and  with  the  gastric  juice  from  the  body  of  the 
stomach  is  therefore  one  of  the  functions  of  the  peristaltic  waves. 
The  resulting  chyme  is  a  soupy,  homogeneous  fluid,  ready  for 
exit  into  the  intestine. 

Another  function  of  the  intimate  contact  of  mucosa  with 
gastric  contents  in  the  pyloric  region  is  that  of  continuing 
gastric  secretion.  As  Edkin's  experiments  proved,  the  con- 
dition for  the  continued  secretion  of  gastric  juice,  after  the 
initial  "  psychic  "  secretion,  lies  in  a  chemical  stimulation  of 
the  gland  cells  through  the  blood-stream.23  The  chemical 
stimulant  given  to  the  blood  is  produced,  not  by  the  mucosa  of 
the  cardiac  end  of  the  stomach,  but  by  that  of  the  pyloric  end. 
And  the  vestibular  mucosa  is  roused  to  activity  by  the  presence 
of  acid,  peptone,  or  sugar  solutions — a  presence  which  is  re- 
peatedly forced  on  the  mucosa  by  the  churning  waves. 

An  associated  function  of  the  churning  action  in  the  vestibule 
is  concerned  with  absorption.  Although  water  is  not  absorbed 
in  the  stomach,  glucose  in  concentrated  solution,  and  proteins 
which  have  been  exposed  to  gastric  digestion,  may  be  absorbed 
in  considerable  amount.24  The  mucosa  of  the  vestibule  has 
many  fewer  glands  than  the  mucosa  of  the  cardiac  end,  where 
they  are  placed  in  very  close  order.  The  absorption  that  occurs 
in  the  stomach,  therefore,  probably  takes  place  in  the  vestibule, 
for  there  the  epithelial  surface  is  most  favourable  to  the  process. 
There  also  gastric  digestion  is  most  advanced,  and  the  food  in 
consequence  is  most  ready  for  passage  through  the  mucosa. 
And,  furthermore,  in  the  vestibule  the  mechanical  conditions 
are  most  favourable  to  absorption,  because  the  digested  food  is 
repeatedly  brought  into  very  close  contact  with  the  mucous  lining. 
If  the  pylorus  does  not  relax  before  an  approaching  wave,  the 
food  is  pressed  into  a  blind  contractile  pouch,  the  only  exit  from 
which  is  backward  through  the  advancing  ring  of  constriction. 
As  we  have  seen,  the  constrictions  are  deeper  near  the  pylorus, 
and  the  rings  therefore  are  small ;  consequently  the  food  is  squirted 
backward  through  them  with  considerable  violence.  The  action 
of  this  part  of  the  stomach  on  the  food  can  be  observed  by  means 
of  the  little  pellets  which  I  have  already  mentioned.  As  the 
slow  waves  push  the  little  morsel  and  the  surrounding  soft  food 
up  to  the  closed  sphincter,  the  whole  mass  is  squirted  back 


THE   EFFECTS    OF   STOMACH   MOVEMENTS  69 

into  the  vestibule.  Again  and  again  I  have  seen  this  process 
repeated  until  the  sphincter  relaxed  and  allowed  the  more  fluid 
parts  to  pass  out.* 

The  older  writers  on  the  physiology  of  digestion  described 
a  selective  action  of  the  pylorus.  The  region  of  the  sphincter 
was  supposed  to  possess  a  peculiar  sensitivity  which  caused  it  to 
prevent  the  passage  of  undigested  material  into  the  duodenum. 
Hofmeister  and  Schutz,  and  Moritz,  have  disclaimed  any  such 
function,  and  have  declared  that  solid  particles  are  carried  from 
near  the  exit  of  the  stomach  back  to  the  cardiac  end  by  anti- 
peristaltic  waves.  The  action  at  the  pylorus  which  I  have  seen, 
however,  was  like  that  described  by  the  older  writers  ;  for  during 
digestion  there  was  no  antiperistalsis,  and  the  sphincter,  separa- 
ting the  fluids  from  the  solids,  as  in  the  case  of  the  hard  morsels 
mentioned  above,  caused  the  solids  to  remain  and  undergo  a 
tireless  rubbing.  Frequently,  when  several  of  these  pellets 
were  given  at  the  same  time,  they  have  all  been  seen  in  the 
vestibule  after  the  stomach  was  otherwise  empty.  There  they 
remained,  to  be  softened  in  time  by  the  digestive  juices  or  to  be 
forced  through  the  pylorus  later,  for,  as  is  well  known,  solids 
do  pass  into  the  intestine.25  It  seems  highly  probable  that  the 
prevalence  of  pathological  conditions  in  the  pyloric  end  of  the 
stomach,  rather  than  in  the  cardiac  end,  is  due  to  the  injury 
which  the  greater  activity  of  the  pyloric  end  may  bring  upon  itself. 

The  presence  of  peristaltic  waves  on  the  right  half  of  the 
stomach  and  their  absence  from  the  left  half  indicates  two  separate 
parts  of  the  stomach.  The  evidence  now  before  us  shows  that 
these  two  parts  have  distinct  functions.  The  left  half  is  a  reser- 
voir in  which  the  food  is  not  mixed  with  the  gastric  secretion, 
and  from  which  the  contents  are  slowly  pressed  out  into  the  active 
right  half.  The  peristaltic  waves  coursing  over  the  right  half 
mix  the  food  with  the  gastric  juice,  expose  it  to  the  mucosa  of 
the  vestibule  for  absorption  and  for  the  continuance  of  gastric 
secretion,  churn  the  unbroken  particles  of  food  until  they  are 
triturated,  and  finally  expel  the  chyme  into  the  duodenum. 
Still  other  consequences  of  the  different  activities  of  the  two 
ends  of  the  stomach  are  next  to  be  considered. 

*  At  a  meeting  of  the  Boston  Society  of  Medical  Sciences,  May  20,  1902,  I 
demonstrated  a  method  of  showing  the  churning  function  of  the  stomach, 
and  the  activities  of  other  parts  of  the  alimentary  canal,  by  means  of  the 
zoetrope. 


70  THE   MECHANICAL   FACTORS    OF   DIGESTION 


REFERENCES. 

1  Kelling,  Ztschr.  f.  Bid.,  1903,  xliv.,  p.  234. 

2  Sick  and  Tedesko,  Deutsches  Arch.  f.  Jdin.  Med.,  1907,  xcii.,  p.  439. 

3  Griitzner,  Ergebn.  d.  Physid.,  1904,  Abth.  ii2.,  p.  77. 

4  Miiller,  Arch.  f.  d.  ges.  PhysioL,  1907,  cxvi.,  p.  253. 

5  Kelling,  loc.  cit.,  p.  181. 

6  v.  Pfungen,  Centralbl.  /.  PhysioL,  1887,  i.,  pp.  220,  275. 

7  Moritz,  Ztschr.  f.  Bid.,  1895,  xxxii.,  pp.  356-358. 

8  Sick,  Deutsches  Arch.  /.  Idin.  Med.,  1906,  Ixxxviii.,  p.  190. 

9  Home,  Lectures  on  Comparative  Anatomy,  London,  1814,  i.,  p.  140. 

0  Eberle,  Physiologic  der  Verdauung,  Wiirzburg,  1834,  pp.  81,  91,  100,  154. 

11  Ellenberger  and  Hofmeister,  Arch.  f.  wissensch.  u.  prakt.  Thierh.,  1882, 
viii.  ;   1883,  ix.  ;   1884,    x.,    p.  6  ;    and  1886,  xii.,  p.   126.      Ellenberger  and 
Goldschmidt,  Ztschr.  f.  physiol.  Chem.,  1886,  x.,  p.  384. 

12  Beaumont,  Physidogy  of  Digestion,  Plattsburgh,  1833,  p.  110. 

13  Cannon,  Am.  J.  PhysioL,  1898,  i.,  p.  377. 

14  Cannon,  Am.  J.  PhysioL,  1898,  i.,  p.  378. 

15  Scheunert,  Arch.  f.  d.  ges.  PhysioL,  1906,  cxiv.,  p.  64. 

16  Griitzner,  Arch.  f.  d.  ges.  PhysioL,  1905,  cvi.,  p.  463. 

17  Cannon,  Am.  J.  PhysioL,  1898,  i.,  p.  379. 

18  Grutzner,  Deutsche  Med.-Ztg.,  1902,  No.  28. 

19  Sick,  Deutsches  Arch.  /.  Jdin.  Med.,  1906-07,  Ixxxviii.,  p.  199. 

20  Prym,  Deutsches  Arch.  f.  klin.  Med.,  1907,  xc.,  p.  310. 

21  Hertz,  Quart.  J.  Med.,  1910,  iii.,  p.  384. 

22  v.  Wittich,  Arch.  f.  d.  ges.  PhysioL,  1874,  viii.,  p.  448. 

23  Edkins,  J.  Physid.,  1906,  xxxiv.,  p.  133. 

24  v.  Mering,  Verhandl.  d.  xii.  Congr.  f.  innere  Med.,  1893,  p.  471  ;  TobJer, 
Ztschr.  f.  physiol.  Chem.,  1905,  xlv.,  p.  206. 

25  Cannon,  Am.  J.  Physid.,  1898,  i.,  p.  377. 


CHAPTER  VII 

THE  STOMACH  MOVEMENTS  IN  RELATION  TO  SALIVARY 
DIGESTION,  AND  GASTRO-ENTEROSTOMY 

THE  discussion  of  the  events  in  the  stomach  has  thus  far  shown 
that  the  contents  may  rest  in  the  cardiac  end  for  an  hour  or  more, 
exposed  to  a  relatively  slight  pressure,  and  unaffected  by  the 
peristalsis  of  the  pyloric  end  ;  and,  on  the  other  hand,  that  the 
contents  of  the  pyloric  end,  repeatedly  swept  to  and  fro  by  the 
passing  waves,  are  repeatedly  exposed  to  a  pressure  which 
increases  as  the  pylorus  is  approached.  These  conditions  have 
important  bearings  on  the  question  of  salivary  digestion  in  the 
stomach,  and  on  the  course  taken  by  the  food  after  the  operation 
of  gastro-enterostomy.  These  matters  we  shall  now  consider. 

SALIVARY  DIGESTION  IN  THE  STOMACH. 

In  stating  the  functions  of  saliva,  emphasis  has  been  laid  on 
its  effects  as  a  lubricant  for  the  tongue,  cheeks,  and  lips,  and 
for  the  food  about  to  be  sent  through  the  oesophagus  ;  and  as 
a  diluent  for  irritating  substances  taken  into  the  mouth.  Saliva 
can  indeed  change  starch  to  sugar  ;  but  during  ordinary  mastica- 
tion the  short  time  for  this  chemical  change  has  been  pointed  out, 
and  in  the  stomach  the  action  of  ptyalin  has  been  supposed  to 
be  soon  stopped  by  the  acid  gastric  juice. 

The  short  time  assumed  for  salivary  digestion  in  the  stomach 
was  supported  by  Beaumont's  conception  that  all  the  food  was 
rapidly  acidified  by  circulation  along  the  gastric  walls.  These 
mixing  currents,  however,  as  we  have  seen,  do  not  exist,  and 
in  the  cardiac  end,  although  the  surface  of  the  contents  becomes 
acid,  the  internal  mass  of  the  contents  remains  unchanged  in 
reaction.  Since  salivary  digestion  can  continue  so  long  as  free 
acid  is  absent,  I  suggested  in  1898  that  salivary  digestion  might 

71 


72  THE  MECHANICAL   FACTOKS    OF   DIGESTION 

proceed  in  the  cardiac  sac  for  an  hour  or  more  without  inter- 
ference by  the  acid  gastric  juice.1  This  conclusion  has  been 
supported  by  Oehl,2  and  by  Heyde,  whose  experimental  work 
with  Griitzner  has  been  described. 

Several  researches  have  been  published  indicating  the  possi- 
bility of  rather  extensive  amylolysis  in  man.  As  long  ago  as 
1880,  von  den  Velden  pointed  out  that  free  hydrochloric  acid 
does  not  appear  for  almost  an  hour  after  eating  an  ordinary 

(breakfast,  and  for  almost  two  hours  after  eating  a  full  midday 
meal.    And,  later,  Hensay3  and  Miiller,4  presented  quantitative 
analyses  of  the  amounts  of  sugar  jmd^dgxtrins  jwhich  might 
be  formed  in  the  stomach  whenlood  is  carefully  chewed.     They 
found  that  after  aTialf^our  in  the  stomach  carbohydrate  food 
/    was  in  large  part  made  soluble  by  saliva,  that  over  one-half, 
I      even  two-thirds,  of  the  soluble  portion  consisted  of  maltose  and 
of  dextrins  closely  related  to  maltose,  and  that  the  remainder 
\     consisted  of  dextrins  more  nearly  related  to  starch. 

None  of  the  observers  who  brought  forward  these  positive 
results  regarded  the  differences  between  the  pyloric  and  cardiac 
ends  of  the  stomach.  To  be  sure,  many  years  ago  Ellen- 
berger  and  Hofmeister  had  studied  the  digestive  processes  in 
the  pyloric  vestibule  and  the  cardiac  sac  of  the  horse  and  pig,5 
and  later  Hohmeier  reported  similar  studies  on  the  rat.6  The 
cardiac  end  of  the  stomach  in  the  horse,  pig,  and  rat,  how- 
ever, is  to  a  great  extent  lined  with  inactive  pavement  epithe- 
lium, and  with  "  cardia  "  glands,  the  secretion  of  which  is  not 
acid.7  A  demonstration  of  salivary  digestion  in  the  cardiac 
end  of  the  stomach  under  these  circumstances  is  not  satisfactory 
proof  of  what  occurs  in  animals  in  which  the  secretion  of  the 
cardiac  wall  is  strongly  acid.  H.  F.  Day  and  I8  undertook, 
therefore,  an  investigation  of  salivary  digestion  in  the  stomach 
of  the  cat,  which  resembles  the  stomach  of  the  dog  and  of  man, 
not  only  in  structure,  but  also  in  pouring  out  an  active  secretion 
from  almost  every  part  of  its  surface. 

Crackers,  free  from  sugar,  were  powdered,  weighed  in  uniform 
amount  (30  grammes),  and  mixed  with  a  uniform  volume 
of  filtered  human  saliva  (100  c.c.).  The  resulting  thick  mush 
was  immediately  fed  in  small  amounts  or  introduced  by  a  tube 
into  the  stomach  of  the  hungry  animal.  At  the  end  of  a  half- 
hour,  an  hour,  one  and  a  half  or  two  hours,  the  animals  were 
quickly  etherized,  and  the  stomach  excised,  after  the  contents 


SALIVARY  DIGESTION  73 

of  the  pyloric  and  cardiac  ends  had  been  separated  by  a  ligature 
tied  around  midway  between  them.  The  contents  of  the  two  ends 
were  at  once  removed,  and  the  enzyme  action  stopped  by  boiling. 
After  the  food  had  evaporated  to  dryness,  it  was  powdered, 
1  gramme  of  it  was  mixed  with  100  c.c.  of  distilled  water,  the 
mixture  was  allowed  to  stand  for  a  half-hour,  then  filtered,  and 
the  filtrate  tested  for  sugar  (as  maltose)  by  Allihn's  method. 

Two  factors,  besides  the  difference  between  the  two  ends  of 
the  stomach,  had  to  be  considered.  One  was  the  rapidity  of 
salivary  digestion.  Starchy  foods  vary  considerably  among 
themselves  in  the  rate  at  which  they  change  to  sugar.9  The 
material  used  by  us  was  tested  in  vitro  at  38°  C.,  and  in  seven 
minutes  four-fifths  of  the  amount  of  sugar  found  at  the  end  of 
an  hour  was  already  present.  Under  these  conditions  the 
accumulation  of  the  products  of  digestion  inhibited  the  action 
of  the  ferment  as  time  passed  ;  nevertheless,  the  change  was 
clearly  of  sufficient  rapidity  to  result  in  considerable  amylolysis 
before  being  checked  by  acid,  even  in  the  pyloric  end.  The 
second  condition  to  be  considered  was  the  possibility  of  any 
agency,  except  saliva,  that  would  change  starch  to  sugar. 
Control  experiments,  in  which  the  powdered  cracker  was  mixed 
with  distilled  water,  revealed  only  the  slightest  trace  of  any 
reducing  action. 

Our  examination  showed  that  after  a  half-hour  the  contents 
of  the  cardiac  and  the  pyloric  ends  of  the  stomach  have  about 
the  same  percentage  of  sugar,  and  that  after  an  hour  the  cardiac 
mass,  because  of  continued  amylolysis,  contains  about  80  per 
cent,  more  sugar,  in  unit  volumes,  than  the  vestibular  mass. 
The  difference  is  doubtless  actually  greater,  for  the  food  in  the 
cardiac  end  is  drier  than  that  in  the  pyloric  end,  and  we  ex- 
amined the  dried  material.  From  an  hour  to  two  hours  after 
feeding,  the  ratio  of  the  sugar  percentages  in  the  two  parts  of 
the  stomach  begins  to  approximate  unity  again.  This  change 
is  probably  due  largely  to  diffusion  of  the  sugar  solution  from 
the  cardiac  to  the  pyloric  contents.  The  possibility  of  this 
diffusion  was  proved  by  feeding  first  salmon  and  later  crackers 
mixed  with  saliva.  At  the  end  of  an  hour  some  of  the  salmon 
taken  from  near  the  surface  in  the  cardiac  end,  fully  1-5  centi- 
metres from  the  stratum  of  crackers,  contained  3  per  cent,  as 
much  sugar  as  the  crackers.  This  diffusion,  however,  did  not, 
in  our  experiments,  remove  to  any  important  degree  the  ptyalin 


74  THE   MECHANICAL   FACTORS    OF  DIGESTION 

from  the  mass  in  the  cardiac  sac,  nor  did  the  position  of  the 
stomach  affect  the  differences  in  sugar  production  in  the  two  parts. 

When  liquid  food  was  given,  and  when  small  amounts  of  food 
were  given,  the  sugar  percentages  in  the  two  parts  of  the  stomach 
were  nearly  the  same.  This  observation,  probably  explicable 
on  the  basis  of  ready  diffusion,  or  uniform  penetration  of  the 
acid  gastric  juice,  has  important  bearings,  for  it  indicates  that 
the  usual  test-meal,  small  in  volume  and  containing  fluid,  becomes 
homogeneous  in  the  two  parts  of  the  stomach,  and  that  therefore 
any  part  of  it,  which  is  taken  for  examination,  is  very  like  any 
other  part. 

Much  of  the  starch  which  was  not  changed  to  sugar  was- 
changed  to  dextrin,  and  thus,  since  dextrin  is  not  readily  fer- 
mented, the  food  was  possibly  saved  to  the  organism.  The 
especial  value  of  this  process  lies  in  its  occurrence  in  greatest 
degree  in  the  midst  of  the  cardiac  contents,  where  hydrochloric 
acid,  which  inhibits  the  action  of  many  of  the  organized  f  erments,. 
does  not  for  some  time  make  its  appearance. 

We  may  conclude  therefore  that,  in  the  early  stages  of  gastric 
digestion,  after  an  ordinarily  bountiful  meal  which  has  been 
properly  masticated,  the  contents  of  the  cardiac  end  of  the 
stomach,  although  undergoing  proteolysis  on  the  surface,  are 
chiefly  subject  to  the  action  of  ptyalin  ;  and,  furthermore,  that 
the  contents  of  the  pyloncT  end,  after  a  brief  stage  of  salivary 
digestion,  are  subject  thereafter  to  strictly  peptic  changes. 
Later,  as  the  contents  of  the  fundus  become  acid,  the  food  in 
the  stomach  as  a  whole  receives  uniform  treatment. 

The  observations  of  Miiller  and  Hensay  on  salivary  digestion 
in  man,  together  with  the  results  obtained  by  Day  and  my- 
self, emphasize  again  the  importance  of  mastication.  A  large 
portion  of  the  food  consists  of  starch.  Only  by  mastication  is 
this  food  properly  broken  up  so  that  a  large  surface  is  exposed 
to  the  action  of  ptyalin.  When  it  has  been  thus  thoroughly  in- 
salivated, it  will  go  far  on  the  way  to  final  digestion,  while 
waiting  to  be  discharged  from  the  stomach. 

THE  MOVEMENT  OF  FOOD  AFTER  GASTRO-ENTEROSTOMY. 

If  the  pyloric  canal  becomes  narrow  or  closed,  or  if  there  is- 
otherwise  delay  in  the  passage  of  food  from  the  stomach,  the 
common  operation  of  making  an  artificial  anastomosis,  or  stoma, 


GASTROENTEROSTOMY  75 

between  the  stomach  and  a  loop  of  small  intestine  is  performed, 
in  order  to  render  the  forwarding  of  the  gastric  contents  possible 
or  more  rapid.  The  assumption  is  that  always  after  gastro- 
enterostomy  there  is  a  change  in  the  course  which  the  food  takes 
in  going  from  the  stomach  into  the  bowel.  Two  questions  of 
interest  arise  with  regard  to  the  effect  of  the  new  opening.  Under 
what  conditions  does  it  induce  an  alteration  in  the  normal 
course  of  the  food  ?  And  if  the  normal  course  of  the  food  is 
changed,  what  are  the  results  ? 

In  much  of  the  surgical  literature  on  gastro-enterostomy,  until 
within  a  few  years,  the  operation  was  conceived  as  a  "  drainage  " 
operation,  and  surgeons  were  careful  to  make  the  stoma  at  the 
most  dependent  point  in  the  stomach.  Involved  in  this  con- 
ception are  the  assumptions  that  the  stomach  is  a  relatively 
passive  bag,  and  that  the  food,  swallowed  in  a  semi-solid  state, 
somehow  becomes  liquid,  and  by  gravity  runs  through  the  new 
hole  into  the  intestine.  Facts  which  we  have  already  considered 
prevent  us  from  giving  ready  credence  to  these  assumptions. 

The  stomach  is  not  at  any  time  during  digestion  in  the  con- 
dition of  a  passive  reservoir ;  the  cardiac  end  is  exerting  a 
positive  pressure,  and,  so  long  as  food  is  present,  the  pyloric 
end  is  the  seat  of  continuous  peristalsis.  The  statement  has 
been  made  repeatedly  in  surgical  writings,  that  a  gastro-enter- 
ostomy midway  in  the  stomach  relieves  the  pylorus  of  the  irrita- 
tion from  food  and  gastric  juices.  It  seems  to  be  assumed  that 
the  region  between  the  new  opening  and  the  pylorus  becomes 
unnecessary  for  digestion,  and  inactive.  There  is  no  reason, 
however,  for  believing  that  peristalsis  does  not  persist  under 
these  circumstances,  and  that  the  food  is  not  thoroughly  churned 
in  the  pyloric  end  in  the  normal  manner.  Although,  in  cases 
of  pyloric  stenosis,  gastro-enterostomy,  of  course,  shortens  the 
time  during  which  peristalsis  and  acid  juices  are  present  in  the 
pyloric  end  of  the  stomach,  we  should  not  deceive  ourselves 
by  the  supposition  that  the  operation  permits  this  region  to 
enjoy  entire  relief  from  either  of  these  disturbing  conditions. 
In  observations  on  animals  in  which  the  stomach  and  gut  had 
been  artificially  joined,  and  the  pylorus  externally  ligated  or 
completely  closed  by  sutures,  I  have  seen  the  waves  passing 
over  the  pyloric  end  without  interruption  for  long  periods. 

Our  previous  consideration  has  shown  that,  as  the  stomach 
empties,  the  most  dependent  point  changes  its  position.  The 


76  THE   MECHANICAL  FACTOKS    OF  DIGESTION 

greater  curvature  of  the  relaxed  or  full  stomach  may  indeed 
reach  considerably  below  the  pylorus,  but  as  the  contents 
disappear,  the  greater  curvature  rises,  and  the  pylorus,  being 
more  or  less  fixed,  then  becomes  the  lowest  point. 

The  argument  may  be  advanced  that  observations  on  a 
normal  animal  do  not  hold  good  for  abnormal  conditions  in 
human  beings.  The  claim  may  be  made  that  the  attachment 
of  the  intestine  to  the  stomach  acts  as  a  drag,  keeping  the  stoma 
at  the  most  dependent  point,  and  that  then  the  stomach  must 
be  merely  a  passive  reservoir  with  its  contents  drained  by  gravity. 
Or  the  point  may  be  urged  that  when  the  stomach  is  dilated, 
toneless,  and  flabby,  it  cannot  act  normally,  and  that  the  part 
observed  to  be  lowest  when  the  abdomen  is  opened  must  remain  so. 

In  this  connection  the  ready  mobility  of  the  intestinal  coils 
may  be  mentioned.  If  the  stomach,  however,  has  been  pur- 
posely attached  to  a  fixed  portion  of  the  gut  in  order  to  make 
the  stoma  permanently  the  most  dependent  point,  or  even  if 
the  new  opening  remains  lowest  because  of  pathological  conditions, 
we  may  reasonably  question  whether  evacuation  is  thereby 
facilitated.  For  in  our  discussion  of  the  doctrinaire  notions 
of  the  shape  of  the  normal  stomach  we  learned  that  the  hydro- 
static conditions  in  the  abdominal  cavity  are  such  that  gravity 
drainage  is  impossible  —  that  when  a  gastro-enterostomized 
stomach  is  filled  with  water  the  water  does  not  run  out  by  itself, 
even  with  the  subject  in  the  upright  position.  In  other  words, 
material  does  not  move  along  the  alimentary  canal  unless  the 
pressure  is  greater  on  one  side  of  it  than  on  the  other. 

What  we  have  learned  regarding  the  pressure  relations  in  the 
stomach  is  pertinent  to  the  present  discussion.  As  we  have 
seen,  peristaltic  waves  are  continuously  passing  over  the  pyloric 
end  so  long  as  food  is  present,  and  on  approaching  the  sphincter 
they  become  deeper  and  deeper  until  they  almost  obliterate 
the  lumen.  Two  results  follow  from  this  peristaltic  activity. 
The  waves  which  force  the  food  repeatedly  against  a  closed 
pylorus  mix  the  food  with  the  gastric  juice,  and  churn  the  mixture 
into  a  fluid  chyme.  The  first  effect  of  the  waves,  therefore,  is 
to  render  the  contents  of  the  pyloric  end  of  the  stomach  more 
liquid,  and  therefore  more  freely  movable  than  the  contents  of 
the  cardiac  end.  The  second  effect  of  the  gradually  deepening 
waves  is  that  the  pressure  within  the  stomach  is  greater  near 
the  pylorus  than  anywhere  else. 


GASTKO-ENTEROSTOMY  77 

The  direct  consequence  of  greater  fluidity  of  food  near  the 
pylorus  and  greater  pressure  on  the  food  at  that  point  is  that 
the  chyme  takes  its  normal  passage  through  the  pylorus,  if  the 
pylorus  is  patent,  rather  than  through  any  artificial  opening. 
This  fact  was  first  determined  by  Kelling,  who  performed  gastro- 
enterostomies  on  dogs  by  all  the  methods  known  to  surgery — 
on  the  anterior  and  posterior  surfaces  of  the  stomach,  with  high 
attachment  of  the  jejunum,  with  low  attachment  of  the  jejunum, 
by  union  with  the  ileum  at  any  part — and  at  the  same  time 
made  a  duodenal  fistula.  He  observed  that  nothing  left  by  the 
stoma,  as  could  be  determined  through  the  duodenal  fistula ; 
all  food,  whether  solid  or  liquid,  emerged  from  the  stomach  by 
way  of  the  pylorus.10  This  observation  was  confirmed  in  X-ray 
studies  by  J.  B.  Blake  and  myself.11  We  made  openings  of 
various  sizes  and  at  various  positions  between  the  stomach  and 
intestine.  When  fluid  boiled  starch  was  given,  this  fluid,  instead 
of  running  through  the  stoma  into  the  intestine,  was  forced  out 
naturally  through  the  pylorus.  Only  two  exceptions  were 
observed  in  our  experience  r  one  in  an  animal  with  the  stoma 
on  the  posterior  wall  of  the  vestibule  close  to  the  pylorus,  and 
the  other  in  an  animal  with  a  large  anterior  stoma  (3  centimetres 
long)  about  halfway  between  the  two  ends  of  the  stomach. 
The  food  left  by  both  exits  ;  but  in  the  latter  case  salmon,  less 
fluid,  went  out  by  the  pylorus  alone.  It  was  not  observed  passing 
through  the  stoma  at  any  time  during  four  and  a  half  hours  after 
feeding. 

In  one  instance  the  pylorus  was  partly  occluded.  A  tape 
was  passed  through  the  walls  of  the  stomach  in  front  of  the 
pylorus  and  tied  ;  then  the  gastric  wall  was  sewed  tightly  over 
the  entrance  and  exit  of  the  tape.  The  food  still  passed  out 
through  the  pylorus.  In  another  instance  a  linen  ligature  was 
tied  snugly  around  the  canal  at  the  pyloric  sphincter.  A  week 
later  liquid  boiled  starch  was  fed,  and,  although  peristaltic 
waves  were  continually  pressing  up  to  the  pylorus,  the  food 
was  seen  passing  out  wholly  by  way  of  the  stoma.  Still  later, 
when  thick  salmon  was  fed,  the  stomach  was  watched  for  the 
first  three-quarters  of  an  hour,  and  again  between  two  and 
two  and  a  half  hours  after  the  feeding.  No  food  was  observed 
going  from  the  stoma,  but  in  small  amounts  it  was  passing  through 
the  pylorus.  At  autopsy  the  ligature  was  found  partially 
embedded,  and  the  pyloric  opening  was  about  0-3  centimetre 


78  THE   MECHANICAL   FACTORS    OF  DIGESTION 

in  diameter.  These  cases  clearly  show  that  even  when  the  pylorus 
is  narrowed  so  as  to  make  difficult  the  passage  of  the  chyme, 
the  chyme  is  forced  into  the  intestine  by  the  natural  way  rather 
than  through  an  opening  remote  from  the  greatest  pressure. 

When  salmon  was  fed,  the  food,  with  the  one  exception  above 
mentioned,  was  never  seen  leaving  the  stomach  by  the  artificial 
opening,  if  the  pylorus  was  patent.  The  salmon,  as  a  more  solid 
food  than  the  starch  paste,  becomes,  as  we  have  seen,  fluid  near 
the  pylorus,  although  remaining  in  its  swallowed  condition  in 
the  cardiac  end.  Naturally,  a  more  fluid  material  under  general 
pressure  should  pass  more  readily  through  an  opening  in  the 
stomach  than  a  drier  and  more  solid  mass.  For  this  reason 
alone  the  chyme  should  go  out  through  the  pylorus  sooner  than 
the  unchymified  food  through  an  opening  in  the  middle  of  the 
stomach.  And  when  this  difference  of  consistency,  favourable 
to  the  pyloric  passage,  is  combined  with  greater  pressure  in  the 
pyloric  region,  the  reasonableness  of  the  results  observed  by 
Kelling  and  by  Blake  and  myself  is  manifest. 

These  results  have  been  further  confirmed  by  Tuffier12  and 
by  Delbet.13  They  have  received  support  also  in  observations 
by  Leggett  and  Maury,14  who  traced  the  course  of  food  by  means 
of  strings  tied  to  little  bags  containing  lead  shot.  As  the 
heavy  weight  must  tend  to  carry  the  bags  to  the  lowest  point, 
the  occasional  first  exit  of  the  string  through  the  stoma,  in 
Maury's  experiments,  should  not  be  wholly  unexpected.  The 
possibility  of  the  anastomotic  opening  rather  than  the  pylorus 
being  at  times  the  path  of  election  cannot,  however,  be  gain- 
said ;  recent  experiments  by  F.  T.  Murphy  and  myself  have 
confirmed  the  earlier  work  with  Blake  in  showing  that  occasionally 
•food  will  take  the  artificial  before  it  will  take  the  natural  course. 
But  there  is  no  doubt,  from  the  wide  range  of  evidence  above 
cited,  that  in  experimental  animals  the  natural  exit  of  the  food 
is  through  the  pylorus,  and  not  through  the  artificial  opening, 
when  both  ways  are  offered. 

The  claim  may  again  be  made  that  the  results  of  these  experi- 
ments, which  were  performed  on  animals,  do  not  apply  to  con- 
ditions in  human  beings,  where  the  stomach  and  intestines  are 
larger  structures,  and  permit  the  establishment  of  larger  open- 
ings. In  this  connection  the  experience  of  Berg  is  of  interest. 
In  1907  he  reported  the  cases  of  two  persons,  who  had  each  an 
accidentally  established  duodenal  fistula,  and  were  losing  a  large 


GASTRO-ENTEROSTOMY  79 

amount  of  food  through  this  unnatural  orifice.15  Berg  made  a 
gastro-enterostomy  in  each  patient,  and  in  one  of  them  also 
tied  the  pylorus.  In  the  latter  case  chyme  ceased  to  be  dis- 
charged. In  the  former  case,  however,  it  continued  passing  out 
through  the  duodenal  fistula.  This  operation  on  a  human  being 
exactly  corresponds  to  Kelling's  experiments  on  dogs,  and  to 
the  studies  by  Delbet,  mentioned  above.  The  conclusion,  there- 
fore, may  be  justly  drawn  that,  if  the  pylorus  is  patent,  the 
gastric  contents  are  forced  out  through  the  natural  passage 
rather  than  through  the  anastomosis. 

On  the  basis  of  the  consideration  just  presented,  Moynihan 
has  concluded  that  gastro-enterostomy  is  most  efficient  only 
when  gross  mechanical  obstruction  exists.  Under  no  circum- 
stances, and  in  compliance  with  no  persuasion,  however  insistent, 
he  has  declared,  is  the  operation  to  be  done  in  the  absence  of 
demonstrable  organic  disease.16 

In  animals  in  which  gastro-enterostomy  had  been  performed, 
and  the  pylorus  had  been  left  unclosed  or  only  partly  occluded, 
Blake  and  I  repeatedly  observed  a  circulation  of  the  food.  The 
food  was  forced  through  the  pylorus,  was  pushed  thence  through 
the  duodenum,  and  driven  into  the  stomach  again  through  the 
stoma.  We  have  watched  animals  a  half -hour  at  a  time,  and 
over  and  over  again  at  short  intervals  during  this  period  food 
has  entered  the  duodenum  from  the  pylorus,  and  gone  through 
the  regular  course,  only  to  merge  once  more  with  the  mass  in 
the  stomach.  Usually  at  these  times  no  food  was  seen  passing 
into  the  intestine  beyond  the  stoma.  It  was  of  interest  and 
of  practical  importance  to  observe  that  the  food  circulated  most 
constantly  when  the  stomach  wall  was  stretched  by  a  large 
amount  of  contents.  The  stretching  separates  the  edges  of  the 
opening  to  which  the  intestine  is  attached,  and  as  the  edges 
separate,  the  intestine  is  drawn  straight  between  them.  Thus 
it  forms  a  flat  cover  to  the  stoma,  becoming,  in  short,  practically 
a  part  of  the  gastric  wall.  In  the  stretching  and  flattening  of 
the  attached  coil  of  intestine,  the  entrances  into  the  lumen  of 
the  gut  are  changed  to  narrow  slits.  These  slits  may,  indeed, 
be  so  much  narrowed  by  pressure  applied  to  them  from  within 
the  stomach  that  they  act  like  valves,  permitting  material  to 
enter,  but  preventing  its  escape. 

The  effectiveness  of  these  "  valves  "  we  tested  in  the  excised 
stomach  by  tying  the  pylorus  and  filling  the  organ  with  water. 


80 


THE   MECHANICAL  FACTORS    OF  DIGESTION 


As  the  gastric  wall  became  stretched  and  the  internal  pressure- 
increased,  almost  no  water  escaped  through  the  stoma  into  the 
intestine.  And  when  the  cardia  was  closed  and  the  stomach, 
and  its  fluid  contents  further  pressed  by  hand,  the  "  valves  " 
were  still  more  effective  in  preventing  leakage  (see  Fig.  5).  Not 
more  than  a  moderate  distension  of  the  stomach  after  gastro- 
enterostomy  seems,  therefore,  an  essential  condition  for  effective 
action  of  the  anastomosis. 

The  circulation  of  the  food  above  described  did  not  in  our 
experiments  result  in  the  symptoms  of  "  vicious  circulation." 
The  animals  never  vomited  in  conse- 
quence of  repeated  entrance  of  food 
from  the  duodenum  into  the  stomach. 
Indeed,  the  observations  of  Boldireff17 
indicate  that  the  presence  of  a  certain, 
amount  of  bile  and  pancreatic  juice  in 
the  stomach  may  be  quite  normal.  And 
Kaiser,  after  citing  numerous  observers- 
who  found  bile  almost  invariably  present 
after  gastro  -  enterostomy  in  human, 
beings,  has  declared  that  he  does  not 
regard  its  presence  there  unfavourably.18" 
Retention  of  food  in  the  stomach, 
with  subsequent  repeated  vomiting,  such 

ENTRANCES    INTO    THE     as  attends  the   so-called  "vicious   cir- 
INTESTINAL   LUMEN  TO    culation  "  after  gastro-enterostomy,  was- 
associated  usually,  in  our  experiments, 
with  obstructive  kinks   and  other  de- 


v 

/ 


FIG.   5. — DIAGRAM   SHOW- 
ING     HOW      STRETCHING 

THE  STOMACH  IN  GASTRO- 
ENTEROSTOMY  MAY 
CAUSE  THE  ATTACHED 
PART  OF  INTESTINE  TO 

BECOME  ALMOST  CON- 
TINUOUS WITH  THE  GAS- 
TRIC WALL,  AND  THE 


BE  CHANGED  TO   MERE 
SLITS. 

S,  stomach;  I,  intestine. 

monstrable  obstacles  to  the  easy  passage 

of  the  food.  In  the  case  of  fatal  kinking  observed  by  us- 
the  trouble  was  invariably  at  the  distal  point  of  that  part 
of  the  intestine  which  was  attached  to  the  stomach.  Sharp 
turns  in  the  intestine  are  normally  straightened  without 
difficulty  by  the  injection  of  material  driven  along  by  peristalsis. 
When  a  kink  forms  immediately  beyond  the  stoma,  however, 
this  force  is  not  at  hand  to  straighten  it,  for  peristaltic  activity 
has  been  abolished  in  the  intestine  proximal  to  the  kink  by 
cutting  the  necessary  circular  fibres.  The  contraction  of  the 
interrupted  circular  muscle  evidently  can  have  no  other  effect 
than  that  shown  in  Fig.  5 — i.e.,  a  shortening  of  the  intestinal 
wall  between  the  attachments  to  the  stomach.  The  only  force 


GASTEO-ENTEROSTOMY  81 

tending  to  obviate  the  kink  is  the  pressure  on  the  food  in  the 
stomach,  which  in  the  cardiac  portion  is  slight.  The  rational 
procedure,  therefore,  is  to  attach  a  narrow  band  of  the  distal  gut 
continuously  to  the  stomach  wall  for  several  centimetres  beyond 
the  stoma.  The  gut  is  thus  kept  straight  throughout  a  distance 
which  permits  peristalsis  to  become  an  effective  force.  From 
clinical  considerations,  Kappeler  has  come  to  the  same  conclusion, 
and  has  recommended  fastening  to  the  stomach  wall  4  to  6  centi- 
metres of  both  the  proximal  and  distal  loops,  for  the  purpose  of 
avoiding  sharp  turns. 

If  gastro-enterostomy  is  performed  when  the  pylorus  is  entirely 
obliterated,  the  new  opening  presents  the  only  outlet  from  the 
stomach.  Under  these  circumstances  an  important  mechanism 
operating  normally  in  the  duodenum  may  become,  to  some 
extent,  impaired.  The  effect  of  acid  chyme  in  causing  a  flow 
of  pancreatic  juice  and  bile  is  now  well  known.  Bayliss  and 
Starling19  found  that  the  action  of  acid  in  causing  a  flow  of 
pancreatic  juice  and  bile  is  not  confined  to  the  duodenum,  but- 
is  effective  in  approximately  the  upper  60  centimetres  of  the 
dog's  intestine.  It  is  probable,  therefore,  that  secretin  is  pro- 
duced at  least  through  the  duodenum  and  jejunum  of  man.  If 
the  anastomosis  is  made  between  the  stomach  and  the  uppermost 
part  of  the  small  intestine,  the  mechanism  for  the  flow  of  these 
important  digestive  juices  would  be  retained. 

With  the  pylorus  closed  and  the  stoma  as  the  only  exit,  one 
might  suppose  at  first  that  the  admixture  of  the  chyme  with 
pancreatic  juice  and  bile  would  be  largely  abolished.  But  that 
need  not  necessarily  be  the  case.  Probably  a  certain  amount  of 
the  pancreatic  juice  and  bile  is  carried  into  the  jejunum  and 
ileum,  and  there  mixed  with  the  food.  Furthermore,  in  our 
X-ray  observations  on  experimental  animals,  the  food  was  re- 
peatedly seen  passing  from  the  stoma  into  the  proximal  loop. 
No  sooner  did  it  thus  pass  towards  the  pylorus  than  a  peristaltic 
wave  was  started  which  swept  the  food  at  once  into  the  stoma 
again.  As  the  circular  fibres  were  not  complete  at  the  stoma, 
the  food  was  not  pressed  past  the  opening  into  the  distal  gut, 
but  was  forced  into  the  stomach.  No  sooner  had  the  wave  gone 
by  than  the  food  was  pressed  again  into  the  proximal  loop. 
Thereupon  a  new  peristaltic  wave  once  more  pushed  the  food 
toward  the  anastomotic  opening ;  back  it  was  pressed  again, 
however,  when  the  wave  reached  the  cut  fibres.  This  process, 

6 


82  THE   MECHANICAL    FACTORS    OF   DIGESTION 

repeatedly  observed,  must  at  least  mix  some  of  the  food  very 
thoroughly  with  the  digestive  secretions  poured  into  the  duo- 
denum. Kelling20  has  recorded  a  surgical  case  in  which  he 
observed  through  a  fistula  a  similar  passage  of  some  of  the  food 
backwards  into  the  duodenum  from  the  stoma.  Only  a  rela- 
tively small  part  of  the  food,  however,  can  be  treated  in  this 
manner,  and  at  best  this  to-and-fro  shifting  is  a  poor  substitute 
for  the  process  which  normally  mixes  the  juices  and  the  chyme 
in  the  first  part  of  the  small  intestine. 

The  observations  on  the  effects  of  gastro-enterostomy  above 
described  affect  the  conclusions  drawn  from  studies  of  digestion 
and  absorption  after  this  operation.  These  conclusions  are 
based  on  figures  obtained  in  some  instances  with  the  pylorus 
patent,  in  other  instances  with  it  occluded.  Possibly  the  wide 
variations  in  the  amounts  of  the  different  foodstuffs,  particu- 
larly fats,  which  have  been  reported  as  not  absorbed  after 
gastro-enterostomy,  may  be  explained  by  the  degree  of  devia- 
tion of  the  chyme  from  its  normal  course  because  of  the  differing 
patency  of  the  pylorus. 

From  the  considerations  suggested  by  our  experimental  work, 
Blake  and  I  concluded  that  the  stoma  should  be  large  and  near 
the  pylorus,  that  circulation  of  the  food  could  be  rendered  less 
likely  by  avoiding  conditions  which  stretch  the  stomach,  and  that 
kinks  might  be  obviated  by  attaching  several  centimetres  of  the 
distal  gut  to  the  stomach.  The  probability  of  a  circulation  of  the 
food,  however,  if  the  pylorus  is  left  open,  the  non-mixture 
of  much  of  the  food  with  the  digestive  and  neutralizing  fluids 
in  the  duodenum,  and  the  ever-present  danger  from  kinks, 
despite  care,  make  the  operation  not  an  ideal  one.  When  pyloro- 
plasty  is  possible,  these  objections  can  be  avoided.  And,  as 
Blake  and  I  pointed  out,  in  accordance  with  our  observations, 
the  rapid  exit  of  food  from  the  stomach  after  cutting  the  pyloric 
sphincter  is  prevented  by  rhythmic  contractions  of  muscle 
rings  in  the  duodenum — an  activity  which  replaces  in  part  the 
functions  of  the  pylorus,  and  also  mixes  the  food  with  the  pan- 
creatic juice  and  bile. 

REFERENCES. 

1  Cannon,  Am.  J.  Physid.,  1898,  i.,  p.  379. 

2  Oehl,  Arch.  Ital.  de  Bid.,  1899,  xxxii.,  p.  114. 

3  Hensay,  Munchen.  med.  Wchnschr.,  1901,  xlviii.,  p.  1208. 

4  Miiller,  Sitzungsb.  d.  phys.-med.  Gesdlsch.  zu  Wiirzlurg,  1901,  p.  4. 


GASTROENTEROSTOMY  83 

5  Ellenberger  and  Hofmeister,  Arch.  /.  wissensch.  u.  praTct.  Thierh.,   1884, 
vii.,  p.  6  ;  and  1886,  xii.,  p.  126. 

6  Hohmeier,  Inaugural-Dissertation,  Tubingen,  1901. 

7  Oppel,  Lehrb.  d,  vergl.  mik.  Anat.  d.   Wirbelthiere,  i.,  Der  Macicn,  Jena, 
1896,  pp.  240,  337,  346,  397. 

8  Cannon  and  Day,  Am.  J.  Physiol.,  1903,  ix.,  p.  396. 

9  Hammarsten,  Jahresb.  ii.  d.  Fortschr.  d.  Thierchem.,  1871,  i.,  p.  187. 

10  Kelling,  Arch.  /.  llin.  Chir.,  1900,  Ixx.,  p.  259. 

11  Cannon  and  Blake,  Ann.  Surg.,  1905,  xli.,  p.  686. 

12  Tuffier,  La  Semaine  Mid.,  1907,  ii.,  p.  511. 

13  Delbet,  Bull,  et  Mini.  Soc.  de  Chir.,  Paris,  1907,  xxxiii.,  p.  1250. 
11  Leggett  and  Maury,  Ann.  Surg.,  1907,  xlvi.,  p.  549. 

15  Berg,  Ann.  Surg.,  1907,  xlv.,  p.  721. 

16  Moynihan,  Brit.  M.  J.,  1908,  i.,  p.  1092. 

17  Boldireff,  Zentralbl.  f.  Physiol.,  1904,  xviii.,  p.  457. 

18  Kaiser,  Ztschr.  /.  Chir.,  1901,  Ixi.,  p.  337. 

19  Bayliss  and  Starling,  J.  Physiol.,  1902,  xxviii.,  p.  325. 

20  Kelling,  Deutsche  Ztschr.  /.  Chir..  1901,  Ix.,  p.  157. 


CHAPTER  VIII 

THE  PASSAGE  OF  DIFFERENT  FOODSTUFFS  FROM  THE  STOMACH 

IN  1901,  while  studying  the  movements  of  the  intestines,  I 
observed  that  not  only  did  salmon  begin  to  leave  the  stomach 
later  than  bread  and  milk,  but  that  it  was  slower  in  reaching 
the  large  intestine  ;  and  in  the  report  of  the  research  I  called  atten- 
tion to  this  interesting  difference.  A  careful  study  of  this 
phenomenon,  and,  in  general,  of  the  manner  in  which  the  different 
foodstuffs  are  mechanically  treated  by  the  alimentary  canal, 
seemed  a  promising  basis  for  understanding  the  agencies  by 
which  the  movements  are  controlled.  Accordingly,  experiments 
were  undertaken,  directed  towards  the  application  of  the  X  rays 
to  the  purposes  of  such  an  investigation.  Since  the  method 
devised  has  proved  serviceable  in  a  variety  of  directions,  I  shall 
describe  it  in  some  detail. 

Among  the  first  essentials  for  simplicity  of  method  in  a  study 
of  the  mechanical  treatment  of  foods  by  the  stomach  and  intes- 
tines is  the  employment  of  foods  as  purely  protein,  fat,  or  carbo- 
hydrate, as  possible.  Such  foods  were  selected.  Boiled  beef  free 
from  fat,  boiled  haddock,  and  the  white  meat  of  fowl,  are  examples 
of  the  proteins  that  were  fed  ;  beef  suet,  mutton  and  pork  fat, 
are  representatives  of  the  fats ;  starch  paste,  boiled  rice,  and 
boiled  potatoes,  of  the  carbohydrates.  A  uniform  amount — 
25  c.c. — was  invariably  given.  The  food  was  always  finely 
broken  or  pressed  in  a  mortar,  and,  if  carbohydrate  or  protein, 
was  moistened  with  enough  water  to  produce,  as  nearly  as  could 
be  judged  by  the  eye  and  by  manipulation,  the  uniform  con- 
sistency of  thick  mush.  Bismuth  subnitrate,  5  grammes, 
thoroughly  mixed  with  each  25  c.c.  amount,  rendered  it  opaque 
to  the  X  rays. 

In  all  cases  full-grown  cats,  deprived  of  food  for  twenty-four 
or  thirty  hours  previous  to  the  experiment,  served  as  subjects 

84 


THE   PASSAGE    OF   DIFFERENT   FOODSTUFFS  85 

for  the  observations.  The  animals  were  either  permitted  to  eat 
from  a  dish,  or  were  placed  on  holders  and  fed  from  a  spoon, 
usually  with  little  or  no  difficulty,  and  released  as  soon  as  fed. 
A  half-hour  and  an  hour  after  the  feeding,  and  thereafter  at 
hourly  intervals  for  seven  hours,  the  animals  were  fixed  in  the 
holders,  observed,  and  the  conditions  recorded.  With  proper 
assistance,  four  or  five  animals  can  be  examined  at  one  sitting. 

The  records  consisted  of  outlines  of  the  shadows  of  gastric  and 
intestinal  contents  traced  on  transparent  paper  laid  on  the  fluor- 
escent screen.  If  in  any  case  there  was  doubt  that  all  the 
shadows  had  been  recorded,  an  electric  light,  flashed  momen- 
tarily on  the  tracing  before  its  removal  from  the  screen,  per* 


FIG.  6. — TRACINGS  or  THE  SHADOWS  OF  THE  CONTENTS  OF  THE  STOMACH 
AND  INTESTINES  MADE  Two  HOURS  AFTER  FEEDING,  IN  ONE  CASE  BOILED 
LEAN  BEEF  (A),  AND  IN  THE  OTHER  BOILED  RICE  (B). 

The  small  divisions  in  some  of  the  loops  represent  rhythmic  segmentation. 

mitted  the  outlines  drawn  on  the  paper  to  be  compared  with  the 
shadows,  and  the  outlines  thus  verified. 

Since  the  diameter  of  the  intestinal  contents  varies  only 
slightly  (see  Fig.  6),  the  area  of  cross-section  of  the  contents 
may  be  disregarded,  and  the  aggregate  length  of  the  shadows 
taken  to  indicate  the  amount  of  food  present.  Thus  by  com- 
,  paring  the  aggregate  length  of  these  shadows  it  is  possible  to 
judge  the  relative  amounts  of  a  food  in  the  intestine  of  an  animal 
at  different  times  after  feeding,  as  well  as  the  relative  amounts 
of  different  foods  in  a  series  of  animals,  or  in  the  same  animal  in 
a  series  of  experiments,  at  any  given  interval  after  the  food  was 
ingested.  For  example,  in  one  case,  the  original  record  of  which 
is  reproduced  in  Fig.  6,  the  protein  in  the  intestine  two  hours 
after  feeding  was  20  centimetres  (the  aggregate  length  of  the 


86  THE   MECHANICAL   FACTORS    OF  DIGESTION 

masses)  ;  and  in  another  case  the  amount  of  carbohydrate,  at 
the  same  time  after  feeding,  and  similarly  measured,  was  43  cen- 
timetres. By  this  method  the  observer,  without  interrupting 
or  interfering  with  the  course  of  digestion,  can  know  when  food 
first  leaves  the  stomach,  the  rate  at  which  different  foods  are 
discharged  into  the  intestine,  the  time  required  for  passage 
through  the  small  intestine,  and  the  mechanical  treatment 
which  the  food  receives.  Only  during  the  brief  periods  of  making 
the  records  are  the  animals  in  any  way  disturbed  ;  between 
observations  they  rest  normally  and  quietly,  wholly  unrestrained. 
That  the  results  obtained  by  the  use  of  the  method  are  not  due 
to  individual  peculiarities  was  proved  by  observing  the  same 
animal  repeatedly  with  different  foods,  and  finding  the  results 
characteristic  of  the  food,  and  not  peculiar  to  the  animal. 
Animals  once  used  were  not  used  again  within  three  days. 

The  method  has  obvious  defects  :  (1)  The  loops  of  intestine 
are  not  always  parallel  with  the  screen,  and  the  loops  not  parallel 
do  not  always  make  the  same  angles  with  the  screen  surface  ; 
the  shadows  cast  by  the  contents  of  the  loops  must  therefore  be 
variously  foreshortened.  In  extenuation  of  this  defect,  it  may 
be  said  that  the  animals  were  stretched  on  their  backs,  and 
that  the  ventral  abdominal  wall  was  flattened,  both  by  the 
stretching  and  by  the  pressure  of  the  fluorescent  screen  laid 
upon  it ;  the  loops  therefore  must  have  been  nearly  parallel 
with  the  screen,  except  at  short  dorso-ventral  turns  from  one 
loop  to  another.  That  the  foreshortening  of  the  shadows  in  the 
loops  and  turns  was  not  a  serious  source  of  error  was  repeatedly 
proved  by  tracings  made  before  and  after  a  rearrangement  of 
the  loops  by  abdominal  massage  ;  the  tracings  showed  that  only 
slight  variations  in  the  aggregate  length  of  the  shadows  resulted. 
(2)  By  overlapping  of  the  loops  two  masses  of  food,  or  parts  of 
two  masses,  may  cast  a  single  shadow.  Care  was  invariably 
taken  to  obviate  this  error  by  pressing  apart  with  the  fingers 
loops  lying  close  together.  (3)  May  not  the  bismuth  subnitrate 
and  the  food  separate,  and  the  shadows  then  be  misleading  ? 
This  separation  doubtless  occurs  to  some  extent  in  the  stomach. 
To  test  the  question  with  reference  to  the  intestinal  contents, 
which  are  much  more  important  for  the  reliability  of  the  method, 
animals  were  fed  the  three  different  kinds  of  food,  and  were 
killed  from  two  to  six  hours  after  the  feeding.  The  intestinal 
mucosa  was  remarkably  free  from  any  perceptible  separate 


. 


THE    PASSAGE    OF   DIFFERENT    FOODSTUFFS  87 


deposits  of  the  heavy  powder,  and  the  well-limited  masses  of 
material  scattered  at  intervals  along  the  gut  were  invariably 
mixtures  of  bismuth  subnitrate  and  the  food.  Naturally,  as 
part  of  the  food  becomes  digested,  and  as  fluids  constantly  inter- 
change between  the  intestinal  mucosa  and  the  food-remnant  in 
its  onward  movement,  the  relation  of  the  bismuth  subnitrate  to 
the  food  must  vary  ;  but  examination  proved  that  the  remnant 
does  not  become  fluid  to  a  degree  which  prevents  it  from  being 
a  vehicle  for  the  transmission  of  the  bismuth  salt,  nor,  on  the 
other  hand,  does  the  percentage  of  bismuth  fall  until  it  no  longer 
indicates  the  presence  of  alimentary  material.  The  changes  in  the 
relation  of  the  bismuth  salt  to  the  food,  from  absorption  of  food 
or  secretion  of  fluids,  are  clearly  much  less  in  the  early  stages  of 
intestinal  digestion,  when  little  absorption  and  digestive  altera- 
tion have  occurred,  than  they  are  later.  The  application  of 
the  method  to  the  determination  of  the  rate  of  discharge  through 
the  pylorus  is  therefore  justified  only  in  the  first  two  or  three 
hours  after  digestion,  before  much  absorption  has  taken  place. 
(4)  The  subjective  differences  between  observers,  the  personal 
equation  in  making  records,  is  another  possible  source  of  error. 
That  Magnus1  and  men  working  with  him,  and  Hedblom2  work- 
ing with  me,  have  employed  the  method  with  no  essential  varia- 
tions from  my  original  results  indicates  that  the  personal  equa- 
tion need  not  be  great.  (5)  The  variations  in  the  thickness  of 
the  food-masses  at  different  times,  and  the  variations  in  the 
individual  rates  of  absorption  of  the  different  foods,  are  two 
other  possible  faults  of  the  method.  These  defects,  however,  must 
be  regarded,  especially  in  the  early  stages  of  intestinal  digestion, 
as  relatively  slight,  compared  with  the  great  and  characteristic 
differences  in  the  amount  of  food  present  in  the  intestine  when 
carbohydrate,  fat,  and  protein  foods,  are  separately  fed.3 

The  time  during  which  various  foods  remain  in  the  stomach 
has  by  some  perverse  chance  come  to  be  regarded  as  an  indica- 
tion of  their  digestibility.  Tables  of  "  digestibility,"  based  on 
this  conception,  have  long  been  published.  Such  a  table  Beau- 
mont4 made  from  observations  on  Alexis  St.  Martin,  and  later 
Leube,5  and  Penzoldt  and  his  pupils,6  studied  by  means  of  the 
stomach-tube  the  duration  of  gastric  digestion  of  various  foods, 
and  tabulated  their  findings.  For  several  reasons,  these  figures 
are  not  satisfactory  for  judging  the  rate  at  which  the  stomach 
is  emptied.  The  observations  were  made  either  on  a  pathological 


83  THE   MECHANICAL   FACTOKS    OF  DIGESTION 

subject  or  on  persons  whose  digestive  processes  had  been  inter- 
rupted by  the  introduction  of  a  stomach-tube.  The  results, 
moreover,  express  merely  the  time  when  the  stomach  was  found 
empty  ;  they  give  no  hint  as  to  the  moment  when  food  first 
passed  the  pylorus,  or  as  to  the  amounts,  large  or  small,  which 
entered  the  intestine  at  any  stage  during  digestion.  Also,  if 
comparisons  are  to  be  made,  the  amount  of  food  given  should 
be  known,  for  a  large  amount  will  evidently  remain  longer  in 
the  stomach  than  a  small  amount.  Beaumont's  records  indicate 
frequent  inattention  to  this  factor,  and  Leube's  observations 
have  the  same  defect.  Although  Penzoldt  and  his  fellow-workers 
recorded  the  amounts,  they  did  not  give  systematically  the 
same  amounts,  and  the  stomach  therefore  was  not  always 
dealing  with  the  same  volumetric  problem.  Furthermore,  these 
investigators  did  not  regard  the  consistency  of  the  food — a  factor 
of  importance,  as  we  shall  later  learn  ;  nor  did  they  attempt  to 
simplify  conditions  by  the  use  of  fairly  pure  foodstuffs,  for  their 
purpose  was  to  discover  how  ordinary  articles  of  diet  were 
treated  in  the  stomach. 

Since  my  purpose  was  to  observe  how  different  foodstuffs, 
other  conditions  remaining  as  nearly  as  possible  the  same,  are 
treated  mechanically  by  the  stomach  and  intestine,  I  selected 
foods  predominantly  fat,  carbohydrate  or  protein,  and  fed  them 
in  uniform  amount  and  consistency.  Differences  of  treatment 
then  might  reasonably  be  associated  with  differences  in  the 
foodstuffs.  We  shall  first  consider  the  results  when  fats  are  fed. 

The  Discharge  of  Fats. — In  selecting  f^t  food,  particular  atten- 
tion had  to  be  paid  to  the  effect  of  temperature  on  consistency  ; 
a  fat,  mushy  at  room  temperature,  might  be  much  too  fluid  at 
body  temperature.  Care  was  taken,  therefore,  to  choose  fats 
or  fatty  tissues  which,  when  mixed  with  bismuth  subnitrate, 
presented  at  body  temperature  about  the  same  degree  of  viscosity 
as  the  carbohydrate  and  protein  preparations. 

The  rate  at  which  fats  leave  the  stomach  may  be  judged  from 
the  curve  of  the  fat-content  of  the  small  intestine  (Fig.  7,  dash 
line),  plotted  from  the  average  figures  of  sixteen  cases  of  fat-feed- 
ing.* The  curve  shows  that  the  emergence  of  the  fat  from  the 
stomach  begins  rather  slowly — in  eight  of  the  sixteen  cases,  indeed, 
nothing  left  during  the  first  half-hour  of  digestion — and  continues 

*  The  figures  which  this  and  other  curves  express  can  be  found  in  the  original 
reports  of  the  investigations. 


THE   PASSAGE    OF  DIFFERENT   FOODSTUFFS 


89 


at  such  a  slow  rate  that  there  is  never  any  great  accumulation 
of  fat  in  the  small  intestine.  Fats  almost  invariably  are  present 
in  the  stomach  during  the  seven  hours  of  observation ;  in  one 
case  an  animal  was  killed  six  hours  after  receiving  25  c.c.  of 
mutton  fat,  and  about  11  c.c.  had  not  yet  departed.  The  long, 
low  curve  is  characteristic.  It  indicates  a  slow  discharge  from 
the  stomach,  approximately  as  slow  as  the  departure  of  the  fat 
from  the  small  intestine  by  absorption  and  by  passage  into  the 
large  intestine. 

How  do  the  results  of  the  X-ray  method  accord  with  other 
evidence  as  to  rate  of  emergence  of  fat  from  the  stomach  ?  In 
1876,  Zawilski,7  while  studying  the  duration  of  the  fat-stream 


FIG.  7. 

These  and  all  other  similar  curves  presented  later  show  the  average  aggregate 
length  of  the  food-masses  in  the  small  intestine  at  the  designated  intervals 
after  feeding.  These  are  the  curves  for  various  fat  foods  (dash  line), 
protein  foods  (heavy  line),  and  carbohydrate  foods  (light  line) — sixteen 
cases  each. 

through  the  thoracic  duct,  was  impressed  by  the  length  of  time 
necessary  to  complete  the  absorption  of  fat.  Three  animals, 
fed  150  grammes  of  fat  mixed  with  other  food,  were  killed  after 
different  intervals  ;  after  five  hours  of  digestion,  100  of  the  150 
grammes  were  still  in  the  stomach,  and  even  after  twenty-one 
hours  10  grammes  were  still  there.  In  the  small  intestine  the 
variation  in  amount  was  only  slight ;  about  10  grammes  were 
found  at  five  hours,  and  about  6  grammes  at  twenty-one  hours. 
While  investigating  the  absorption  of  fatty  acids,  Frank8  con- 
firmed the  observations  of  Zawilski :  the  fat  stayed  long  in  the 
stomach,  and  a  fairly  uniform  amount  was  present  at  various 
times  in  the  small  intestine.  And,  again,  in  observations  inci- 
dental to  another  investigation,  Matthes  and  Marquadsen9  con- 


90  THE   MECHANICAL   FACTORS    OF  DIGESTION 

firmed  the  statements  of  Zawilski  and  Frank.  The  testimony 
of  different  observers  was  thus  far  harmonious.  Thereupon 
Strauss  denied  that  fat  remains  long  in  the  human  stomach.10 
His  methods,  however,  were  hardly  comparable  with  those  of 
the  previous  investigators ;  only  one-fourth  of  the  food  was  fat, 
it  was  given  with  much  liquid,  the  observations  were  few,  and  on 
only  one  patient. 

The  results  obtained  by  the  X-ray  method,  therefore,  agree 
with,  and  amplify,  the  evidence  offered  by  Zawilski,  Frank,  and 
Matthes  and  Marquadsen.  The  long  delay  of  fat  in  its  passage 
through  the  alimentary  canal  occurs  in  the  stomach.  Fat 
passes  from  the  stomach  about  as  rapidly  as  the  small  intestine 
disposes  of  it ;  as  a  rule,  therefore,  the  amount  of  fat  in  the  small 
intestine  is  fairly  constant  in  quantity  and  relatively  slight  in 
amount. 

The  Discharge  of  Carbohydrates. — The  rate  at  which  carbo- 
hydrates leave  the  stomach  can  be  judged  from  the  curve  (Fig.  7, 
light  line),  particularly  during  the  first  two  hours  of  digestion. 
In  my  first  observations  on  the  movements  of  the  stomach, 
bread  was  seen  in  the  duodenum  about  ten  minutes  after  feeding. 
The  curve  representing  the  content  of  the  small  intestine  after 
feeding  carbohydrates  shows  that  this  early  emergence  of  the 
starchy  food  from  the  stomach  is  followed  by  an  abundant  dis- 
charge. In  a  half -hour  the  amount  of  carbohydrate  present 
has  almost  equalled  the  maximum  for  fat,  and  at  the  end  of  an 
hour  that  amount  has  more  than  doubled.  The  abrupt  high 
rise  of  the  curve  to  a  maximum  at  the  end  of  two  hours  indicates 
the  great  rapidity  of  discharge.  And  as  the  stomach  was 
usually  almost  empty  about  three  hours  after  feeding  the  standard 
amount  of  carbohydrates,  the  slow  fall  in  the  curve  during  the 
last  four  hours  of  observation  records  in  the  main  the  gradual 
departure  of  the  food  from  the  small  intestine  through  the 
absorbing  wall  and  into  the  colon. 

The  testimony  of  Penzoldt  and  his  pupils,11  that  the  delay  in 
discharge  of  carbohydrates  from  the  human  stomach  is  usually 
not  great,  is  in  harmony  with  the  more  detailed  observations  on 
experimental  animals.  That  potato  leaves  the  human  stomach 
rapidly,  and  that  the  gastric  juice  cannot  attack  it  to  any 
extent,  Marbaix  reported12  in  1898,  and  he  suggested  that  an  im- 
portant question  lies  here.  The  answer  to  that  question  we  must 
soon  consider.  For  the  present  we  need  only  note  that  all  the 


THE   PASSAGE    OF  DIFFERENT    FOODSTUFFS  91 

evidence  for  a  rapid  passage  of  carbohydrate  food  through  the 
pylorus  is  concordant.  As  a  consequence  of  this  rapid  exit  the 
small  intestine  receives  a  large  bulk  in  a  relatively  short  time. 
The  Discharge  of  Proteins. — The  heavy  line  in  Fig.  7  is  a  curve 
plotted  from  the  average  figures  for  the  content  of  the  small 
intestine  after  feeding  four  representative  proteins  in  sixteen 
cases.  The  striking  feature  of  the  protein  curve  during  the  first 
two  hours  is  its  very  slow  rise.  In  nine  of  the  sixteen  cases  no 
food  had  left  the  stomach  at  the  end  of  the  first  half-hour,  and  in 
eight  cases  the  small  intestine  had  not  received  at  the  end  of 
an  hour  more  than  4  centimetres  of  food. 

The  main  portion  of  a  diet  is  more  likely  to  be  composed  of 
carbohydrates  or  proteins,  or  of  the  two  combined,  than  of  fats 
alone.  To  digest  a  diet  consisting  chiefly  or  even  largely  of  fat 
is  an  unusual  task  for  the  digestive  apparatus.  The  mechanical 
treatment  of  carbohydrates  and  proteins  is  therefore  of  more 
importance  practically  than  the  treatment  of  the  fats  ;  and  the 
fact  that  the  stomach  is  more  habituated  to  the  presence  of 
carbohydrates  and  proteins  in  large  amounts  makes  a  con- 
sideration of  the  differences  of  treatment  of  these  foodstuffs 
more  significant  than  a  comparison  involving  the  fats. 

The  curves  representing  the  carbohydrate  and  protein  dis- 
charge from  the  stomach  are  strikingly  different.  At  the  end  of 
a  half-hour  the  average  figures  indicate  that  eight  times  as  much 
carbohydrate  as  protein  has  left  the  stomach  ;  at  the  end  of  an 
hour  more  than  five  times  as  much,  and  even  at  the  end  of  two 
hours,  when  much  carbohydrate  food  has  probably  been  absorbed, 
considerably  more  than  twice  as  much  carbohydrate  as  protein 
is  present  in  the  small  intestine. 

The  remarkable  difference  between  the  carbohydrate  and  the 
protein  rapidity  of  departure  from  the  stomach  assumes  special 
significance  when  the  action  of  gastric  juice  on  these  two  food- 
stuffs is  considered.  That  the  carbohydrates,  which  are  not 
digested  by  the  gastric  juice,  should  begin  to  leave  the  stomach 
soon  after  being  swallowed,  and  should  pass  out  rapidly  into  a 
region  where  they  are  digested,  whereas  the  proteins,  which  are 
digested  by  the  gastric  juice,  should  be  retained  in  the  stomach 
sometimes  for  a  half-hour  or  more,  without  being  discharged 
in  any  considerable  amount,  indicates  the  presence  of  an 
important  digestive  mechanism. 


92 


THE   MECHANICAL   FACTOKS    OF   DIGESTION 


With  the  purpose  of  securing  further  evidence  of  the  action  of 
this  probable  mechanism,  various  combinations  of  foodstuffs 
were  fed,  and  the  rate  of  passage  from  the  stomach  studied  by 
the  method  already  described. 

The  Discharge  when  Carbohydrate  or  Protein  is  Fed  First. — As 
we  have  learned,  when  different  kinds  of  foods  are  fed  one  after 
another,  the  first  food  swallowed  fills  the  pyloric  vestibule  and  lies 
along  the  greater  curvature  of  the  stomach,  and  the  later  food  is 
pressed  into  the  midst  of  that  part  of  the  earlier  food  which 
occupies  the  cardiac  end.  Thus,  if  carbohydrates  are  fed  first 
cm  and  proteins  second,  the  carbo- 

hydrates will  be  in  contact  with  the 
pylorus  and  will  predominate  in 
the  pyloric  end  of  the  stomach, 
while  the  proteins  will  be  found 
in  larger  amounts  towards  the 
fundus. 

Does  the  presence  of  proteins  in 
the  cardiac  end  of  the  stomach 
retard  the  exit  of  carbohydrates 
lying  near  the  pylorus  ?  Or  if  the 
proteins  are  near  the  pylorus,  does 
the  presence  of  the  carbohydrates 
in  the  cardiac  end  cause  an  early 
exit  ?  To  answer  these  questions, 
12-5  c.c.  of  crackers  and  water,  and 
12-5  c.c.  of  boiled  lean  beef,  each 
mixed  with  2-5  grammes  of  sub- 
nitrate  of  bismuth,  were  fed — in  one 


Ml 

•60 
20 
10 

Box 

^ 

^ 

/ 

/ 

\  —  ' 

/ 

'/ 

f. 

~'~~f 

;--• 

// 

^^ 

',*•' 

// 

/ 

/ 

/,, 

'  / 

£ 

'..- 

' 

ITS  i     1           2           3           • 

FIG.  8. 

The  heavy  line  is  the  curve  after 
feeding  moistened  crackers 
first,  lean  beef  second  (four 
cases)  ;  the  heavy  dot  line, 
after  feeding  lean  beef  first, 
crackers  second  (four  cases). 
The  light  line  is  the  curve  for 
crackers  alone,  the  light 
dot  line  for  lean  beef  alone 
(four  cases  each). 


series,  crackers,  then  beef  ;  in  another  series,  beef,  then  crackers. 
The  results  are  represented  in  Fig.  8.  The  rate  of  discharge 
when  carbohydrates  were  fed  first  should  be  compared  with  the 
rate  when  proteins  were  fed  first.  When  the  crackers  were  near 
the  pylorus,  the  discharge  for  two  hours  was  almost  as  rapid  as 
when  crackers  alone  were  given.  At  the  end  of  two  hours, 
however,  the  curve  ceased  to  follow  the  normal  for  crackers; 
there  was  a  checking  of  the  outgo  from  the  stomach,  which  is 
reasonably  explained  by  assuming  that  the  beef  by  that  time  had 
come  to  the  pylorus  in  considerable  amount,  and  was  as  usual 
passing  out  slowly.  On  the  other  hand,  when  the  beef  was  first 
at  the  pylorus,  the  curve  was  in  close  approximation  to  the 


THE   PASSAGE    OF  DIFFERENT   FOODSTUFFS 


93 


40 


30 


20 


10 


normal  for  beef  during  the  first  four  hours,  and  after  that  time, 
as  the  crackers  came  to  the  pylorus  in  greater  amount,  the  curve 
continued  to  rise,  while  the  curve  for  beef  alone  fell.  In 
this  combination,  never  during  the  first  three  hours  was 
there  half  as  much  food  in  the  small  intestine  as  when  crackers 
alone  were  fed.  The  presence  of  protein  near  the  pylorus  dis- 
tinctly retarded  the  onward  passage  of  carbohydrate  food  lying 
in  the  cardiac  end. 

It  is  noteworthy  that  when  beef  was  fed  first  the  stomach  still 
contained  considerable  food  even  six  hours  after  feeding — three 
hours  longer  than  the  period  for  carbohydrates  alone.  On  the 
other  hand,  when  crackers  were  fed  first, 
most  of  the  food  had  left  the  stomach 
at  the  end  of  four  hours — only  about  an 
hour  longer  than  the  carbohydrate 
period.  Since  gastric  peristalsis  persists 
while  food  is  present  in  the  stomach, 
this  experiment  seems  to  indicate  that 
serving  the  cereal  before  the  meat  at 
breakfast,  and  the  old  custom  of  eating 
the  pudding  before  the  beef,  are  rational 
and  physiologically  economic  arrange- 
ments. If  the  carbohydrate,  however, 
follows  the  protein,  careful  chewing,  as 
we  have  learned,  will  permit  salivary 
digestion  to  continue  in  the  cardiac  mass 
during  the  period  of  delay. 

The  Discharge  when  Mixtures  are  Fed. 
— Inasmuch  as  what  we  eat  is  generally 

a  mixture  of  the  various  foodstuffs,  it  was  of  interest  to 
discover  what  effect  combinations  of  the  foods,  from  which 
characteristic  curves  had  been  secured,  might  have  upon  those 
curves.  For  this  purpose,  carbohydrates,  fats,  and  proteins, 
were  mixed  in  pairs,  in  equal  amounts,  to  make  25  c.c.  of  food, 
and  this  mixture,  with  5  grammes  bismuth  subnitrate,  was  fed, 
and  the  results  recorded. 

To  test  the  effect  of  mixing  carbohydrate  and  protein  on 
the  rate  of  gastric  discharge,  equal  parts  of  lean  beef  and 
crackers  were  given.  In  Fig.  9  a  comparison  is  presented 
between  the  treatment  of  the  mixed  foods  and  the  same  foods 
fed  separately.  Only  the  changes  during  the  first  three  hours 


o    \   i         2         3 

Hours 

FIG.  9. 

The  dash  line  is  the  curve 
for  equal  parts  of  moist- 
ened crackers  and  boiled 
lean  beef,  the  heavy 
line  for  crackers  alone, 
and  the  light  line  for 
beef  alone  (four  cases 
each). 


94 


THE   MECHANICAL   FACTORS    OF  DIGESTION 


20 


"     >,     1  2  3  4 

Hours 

FIG.  10. 

The  heavy  line  is  the  curve  for 
lean  beef  alone,  the  light  line 
for  beef  suet,  the  dash  line  for 
a  mixture  of  beef  and  suet  in 
equal  parts  (four  cases  each). 


are  taken  for  consideration,  since  they  are  most  significant  in 
judging  the  rapidity  with  which  the  stomach  empties.  The 
amount  of  the  mixed  food  in  the  small  intestine  at  the  end  of  a 

half-hour  was  nearer  the  carbo- 
hydrate than  the  protein  figure, 
but  in  general,  as  the  curves  show, 
a  mixture  of  carbohydrate  and 
protein  foods  in  equal  parts  resulted 
in  a  rate  of  discharge  which  was 
intermediate :  the  mixed  food  did 
not  leave  the  stomach  so  slowly  as 
the  proteins,  nor  so  rapidly  as  the 
carbohydrates.  This  conclusion 
was  verified  by  obtaining  similar 
results  when  boiled  haddock  and 
mashed  potato  were  mixed  and  fed. 

Boiled  lean  beef  and  beef  suet  mixed  in  equal  amounts  served 
for  observations  on  the  effect  of  combining  fat  and  protein. 
Comparison  of  the  curve  for  the  mixture  with  the  curves  for  the 
two  constituents  fed  separately  (Fig.  10)  reveals  at  once  that  the 

combination  is  discharged  more 
slowly  than  either  the  lean  beef  or 
the  suet  fed  alone.  In  other  words, 
the  presence  of  fat  causes  protein 
to  leave  the  stomach  even  more 
slowly  than  the  protein  by  itself 
would  leave.  Feeding  haddock  and 
mutton  fat  in  equal  parts  corrobo- 
rated the  other  observations  ;  after 
two  hours  the  small  intestine  had 
only  two-thirds  as  much  of  the 
mixed  food  as  of  the  haddock  when 
fed  alone.  The  long  delay  in 
the  initial  passage  of  salmon 
from  the  stomach  (which  con- 
trasted so  strikingly  with  the  rapid 
discharge  of  bread,  and  suggested 

the  investigation)  was  probably  due  to  the  presence  in  salmon 
of  more  than  half  as  much  fat  as  protein. 

Mashed  potato  and  mutton  fat,  and  moistened  crackers  and 
beef  suet,  mixed  equally  in  each  combination,  were  used  in  study- 


40 


•20 


10 


/\ 


Hours 
FIG.  11. 

The  light  line  is  the  curve  for 
mashed  potato,  the  heavy  line 
for  mutton  fat,  and  the  dash 
line  for  mixed  potato  and 
mutton  fat  (four  cases  each). 


THE   PASSAGE    OF   DIFFERENT    FOODSTUFFS  95 

ing  the  effect  of  uniting  fats  and  carbohydrates.  In  each  series 
of  observations  the  passage  of  the  mixed  food  from  the  stomach 
was  more  rapid  at  first  than  the  normal  for  the  carbohydrate  used 
(see  Fig.  11).  Very  soon,  however,  the  fats  had  a  retarding  effect 
on  the  outgo  of  the  carbohydrate,  so  that  the  curve  for  the  mixed 
foods  after  the  first  hour  ceased  to  rise,  and  never  even  approxi- 
mated the  height  of  the  carbohydrate  curve.  We  may  reason-  -^ 
ably  conclude,  therefore,  that  the  addition  of  fat  in  large  amount 
(50  per  cent.)  to  carbohydrate  has  the  same  effect,  though  not  to 
so  great  a  degree,  as  the  addition  of  fat  to  protein  :  the  fat  retards 
the  exit  of  either  foodstuff  from  the  stomach  into  the  intestine. 
The  striking  differences  in  the  rapidity  of  discharge  of  different 
foods  from  the  stomach,  the  importance  of  which  I  need  not 
emphasize,  can  all  be  explained  quite  simply  when  we  under- 
stand the  remarkable  mechanism  of  the  pyloric  sphincter. 


REFERENCES. 

1  Magnus,  Arch.  f.  d.  qes.  Physid.,  1908,  cxxii.,  pp.  210,  251,  261 ;  Padtberg, 
ibid.,  1909,  cxxix.,  p.  476. 

2  Hedblom  and  Cannon,  Am.  J.  Med.  Sc.,  1909,  cxxxviii.,  p.  505. 

3  Cannon,  Am.  J.  Physid.,  1904,  xii.,  p.  387. 

4  Beaumont,  The  Physidogy  of  Digestion,  Plattsburgh,  1833,  p.  269. 

5  Leube,  Ztschr.  f.  Uin.  Med.,  1883,  vi.,  p.  189. 

6  Penzoldt,  Deutsches  Arch.  /.  Uin.  Med.,  1893,  li.,  p.  545. 

7  Zawilski,  Arb.  a.  d.  physid.  Anst.  zu  Leipzig,  1876,  p.  156. 

8  Frank,  Arch.  /.  Physid.,  1892,  p.  501. 

9  Matthes  and  Marquadsen,  Verhandl.  d.  Cong.  f.  innere  Med.,  1898,  xvi., 
p.  364. 

10  Strauss,  Ztschr.  f.  didt.  u.  physikal.  Therap.,  1899,  iii.,  p.  279. 

11  Penzoldt,  Deutsches  Arch.  f.  Uin.  Med.,  1893,  li.,  pp.  549,  559. 

12  Marbaix,  La  Cellule,  1898,  xiv.,  p.  299. 


CHAPTER  IX 
THE  ACID  CONTROL  OF  THE  PYLORUS 

CLINICAL  studies  with  the  stomach-tube,1  investigations  through 
duodenal  fistulas,2  and,  as  we  have  already  seen,  X-ray  observa- 
tions on  the  undisturbed  subject,  combine  to  prove  that  the 
stomach  is  emptied  progressively  during  the  course  of  gastric 
digestion,  and  not  suddenly  at  the  end,  as  some  investigators 
have  stated.3  The  X-ray  studies  and  the  examinations  through 
duodenal  openings  have  further  demonstrated  that  the  chyme 
does  not  pass  through  the  pylorus  at  the  approach  of  every 
peristaltic  wave,  but  emerges  occasionally,  at  irregular  intervals. 
The  irregular  opening  of  the  pyloric  passage  after  periods  lasting 
from  ten  to  eighty  seconds  I  noted  in  my  first  report  of  gastric 
movements,4  and  these  results  were  in  close  agreement  with  the 
observations  of  Hirsch  and  others  on  dogs  with  duodenal  fistulas, 
that  chyme  comes  from  the  stomach  at  intervals  varying  between 
one-fourth  of  a  minute  and  several  minutes.5 

Both  mechanical  and  chemical  agencies  have  been  invoked  to 
explain  the  emptying  of  the  stomach.  These  agencies  have  been 
supposed  by  some  investigators  to  act  in  the  stomach,  by  others 
to  act  in  the  intestine. 

That  mechanical  agencies  acting  in  the  stomach  control  the 
exit  of  food  has  been  claimed  by  those  who  believe  that  chyme  is 
discharged  only  after  several  hours  of  gastric  digestion.  They 
declare  that  the  pyloric  sphincter,  although  able  to  withstand 
the  repeated  peristaltic  pressure  in  the  earlier  stages  of  chymifica- 
tion,  is  overcome  by  the  more  intense  constrictions  in  the  later 
stages.6  We  know,  however,  that  a  delay  of  several  hours  in 
the  discharge  from  the  stomach  is  abnormal.  The  moving  con- 
striction rings  do  indeed  press  deeper  into  the  gastric  contents 
as  digestion  proceeds,  but  this  late  augmentation  of  contraction 
does  not  explain  the  normal  gradual  exit  during  earlier  stages  of 

96 


THE  ACID  CONTKOL  OF  THE  PYLORUS       97 

chymification,  when  wave  after  wave  passes,  with  fairly  uniform 
depth,  and  yet  every  now  and  then  some  chyme  departs.  The 
occasional  discharge  of  chyme  from  the  stomach  cannot  there- 
fore be  attributed  to  an  occasional  increase  of  intensity  of  the 
peristaltic  constrictions. 

The  effect  of  mechanical  conditions  in  the  intestine  on  gastric 
evacuation  was  first  pointed  out  in  1897  by  v.  Mering,7  who 
found  that  the  introduction  of  a  large  amount  of  milk  into  a 
duodenal  fistula  checked  the  exit  of  water  from  the  stomach. 
The  next  year  Marbaix8  published  a  paper  on  evacuation  of  the 
stomach  as  affected  by  a  state  of  repletion  of  various  parts  of 
the  intestine.  A  state  of  repletion  in  the  upper  half  of  the  small 
intestine  induced  by  injections  through  fistulas  inhibited  the 
discharge  from  the  stomach.*  In  order  to  cause  the  reflex, 
however,  even  in  the  first  fourth  of  the  intestine,  the  injected 
liquid  had  to  occupy  a  considerable  extent  of  gut.  For  example, 
filling  the  gut  from  10  to  25  centimetres  beyond  the  pylorus 
caused  no  inhibition  of  the  discharge.  But  much  less  than 
15  centimetres  of  continuous  content  is  normally  present  in 
the  upper  intestinal  tract.  The  tracings  of  X-ray  shadows 
(see  Fig.  6,  p.  85)  show  that  the  intestinal  contents  are  normally 
disposed  in  separate  short  masses.  Under  natural  conditions, 
therefore,  the  extensive  uninterrupted  surface  of  contact  re- 
quired by  v.  Mering's  and  Marbaix's  explanation,  in  order  to 
prevent  a  continuous  outpouring  from  the  stomach,  does  not 
exist.  As  the  continuous  outpouring,  nevertheless,  does  not 
occur,  their  results  do  not  explain  the  normal  'control  of  gastric 
discharge.  Von  Mering's  and  Marbaix's  contribution  has  been 
supported,  however,  by  Tobler's  observation9  that  the  rapid 
inflation  of  a  balloon  in  the  duodenum  checks  the  passage  of 
food  from  the  stomach.  This  experiment,  like  v.  Mering's  and 
Marbaix's,  does  not  explain  normal  conditions,  because,  as  I 
have  shown,10  chyme  normally  gathers  in  the  duodenum 
gradually,  by  repeated  small  additions,  and  even  when  accu- 
mulated lies  as  a  slender  strand  which  does  not  distend  the  gut. 
Each  strand  thus  formed  is  soon  hurried  forward  some  distance 
along  the  tube,  thus  clearing  the  duodenum  for  new  accumulations. 

*  An  investigation  of  the  motor  functions  of  the  stomach  after  pyloroplasty 
(see  Cannon  and  Blake,  Ann.  Surg.,  1905,  xli.,  p.  707)  has  proved  that,  although 
the  upper  part  of  the  small  intestine  may  become  filled  with  food,  there  is 
no  cessation  of  peristalsis.  The  effect  noted  by  v.  Mering  and  Marbaix  is 
therefore  probably  due  to  closure  of  the  pylorus. 

7 


98  THE   MECHANICAL   FACTORS    OF  DIGESTION 

Though  the  passage  of  food  from  the  stomach  may  be  checked 
by  artificially  filling  a  long  piece  of  the  upper  intestine  or  by 
sudden  distension  of  the  gut  at  one  point,  such  conditions  cannot 
account  for  any  natural  control  of  gastric  discharge  from  the 
intestinal  side,  because  such  conditions  are  not  normally  found. 
The  evidence,  therefore,  is  opposed  to  the  conception  that 
mechanical  agencies,  acting  either  in  the  stomach  or  in  the 
intestine,  play  an  important  part  in  controlling  the  normal 
gastric  evacuation. 

We  turn  now  to  a  consideration  of  chemical  agencies  that  have 
been  invoked  to  explain  the  emptying  of  the  stomach.  As  long 
ago  as  1885  Ewald  and  Boas  found,11  by  use  of  the  stomach- 
tube  on  man,  that  there  was  a  considerable  development  of 
free  hydrochloric  acid  before  the  gastric  contents  began  to  be 
notably  diminished  in  amount.  Where  the  acid  may  have  had 
its  effect — whether  on  peristalsis  or  on  the  pyloric  sphincter — 
was  not  determined.  Later,  Penzoldt,12  in  studying  the  periods 
during  which  various  common  foods  remain  in  the  stomach, 
noted  that  foods  delaying  the  appearance  of  free  hydrochloric 
acid  remain  longest.  Verhaegen,13  on  the  other  hand,  declared 
that  it  matters  little  for  the  passage  through  the  pylorus  whether 
the  food  is  acid  or  neutral.  Although  Penzoldt 's  careful  work 
was  of  clinical  value,  it  is  inadequate  to  explain  the  factors 
in  control  of  gastric  evacuation.  The  varying  composition 
of  the  foods  he  used,  the  varying  amounts  and  consistencies, 
and  the  failure  of  his  method  to  indicate  the  rapidity  of 
gastric  discharge  as  digestion  proceeds,  render  difficult  the 
drawing  of  exact  conclusions  from  Penzoldt's  results.  In 
the  presence  of  strong  opposing  evidence,  Verhaegen's  con- 
tention that  neither  acidity  nor  neutrality  of  the  chyme  has 
any  effect  on  the  emptying  of  the  stomach  may  reasonably 
be  doubted.  Furthermore,  his  observations  were  made  with 
the  stomach- tube,  on  only  four  individuals,  two  of  whom 
were  pathologic. 

The  first  evidence  of  the  action  of  chemical  agencies  in  the 
duodenum  on  the  emptying  of  the  stomach  was  brought  forward 
by  Hirsch.  In  1893  he  reported14  that  solutions  of  inorganic- 
acids  left  the  stomach  slowly,  and  he  inferred  that  the  slow  exit 
was  due  to  the  stimulating  effect  of  the  acid  on  the  mucosa  of 
the  duodenum.  Later,  Serdjukow,  one  of  Pawlow's  students, 
inhibited  gastric  evacuation  by  introducing  acid  into  the  duo- 


THE  ACID  CONTROL  OF  THE  PYLORUS       99 

denum  through  a  fistula,15  thus  confirming  the  conclusion  of 
Hirsch.  Tobler's  results16  also  substantiate  it. 

The  main  defect  of  the  above  methods  as  means  for  deter- 
mining the  nature  of  the  chemical  control  of  gastric  discharge  is 
their  failure  to  distinguish  between  the  two  factors  concerned 
in  emptying  the  stomach :  one,  the  pressure  to  which  the  food 
at  the  pylorus  is  subjected  by  recurring  peristaltic  waves  ;  the 
other,  the  action  of  the  pyloric  sphincter.  Not  until  the  X-ray 
method  was  used  was  it  possible  to  watch,  under  normal  con- 
ditions, both  gastric  peristalsis  and  the  exit  of  food  through  the 
pylorus.  Until  the  application  of  the  X-ray  method,  therefore, 
a  clear  distinction  between  the  normal  effects  of  these  two  factors 
could  not  be  made. 

Evidently  the  normal  exit  of  food  might  be  occasional  because 
of  occasional  peristaltic  constrictions,  or  occasional  specially 
strong  peristaltic  constrictions,  pressing  the  gastric  contents 
against  an  easily  opened  pylorus  ;  or,  on  the  other  hand,  the 
occasional  passage  might  be  due  to  an  occasional  relaxation  of 
the  pylorus  in  the  presence  of  fairly  uniform  conditions  of 
pressure. 

Some  of  the  investigators  whose  work  has  already  been  men- 
tioned have,  indeed,  ascribed  the  control  of  gastric  discharge 
solely  to  the  action  of  the  pyloric  sphincter.  Marbaix,  for 
example,  writes  of  the  influence  of  the  repletion  of  the  intestine 
on  the  closure  of  the  pylorus.17  His  evidence  for  this  limitation 
is  not  clear.  Von  Mering,  on  the  other  hand,  recognized  that 
intestinal  repletion  might  check  gastric  discharge  by  stopping 
peristalsis,  and  he  resected  the  pylorus  in  order  to  differentiate, 
if  possible,  between  the  peristaltic  and  the  pyloric  factors.* 
The  failure  to  make  this  differentiation  is  the  essential  flaw,  for 
the  present  analysis,  in  the  methods  of  Ewald  and  Boas,  Pen- 
zoldt,  Hirsch,  Serdjukow,  and  Tobler.  Their  results,  therefore, 
while  significant,  cannot  serve  for  a  conclusive  determination  of 
the  control  of  gastric  evacuation. 

The  evidence  that  under  normal  conditions  peristaltic  waves 
are  continuously  running  over  the  stomach,  so  long  as  food 

*  The  possible  confusion  of  the  two  factors  is  illustrated  in  Pawlow's  report 
of  Serdjukow's  experiments.  He  states  (The  Work  of  the  Digestive  Glands, 
London,  1902,  p.  165)  that  acid  chyme  entering  the  duodenum  reflexly  occludes 
the  pyloric  orifice,  "  and  at  the  same  time  reflexly  inhibits  the  propulsive 
movements  of  the  organ  (stomach)."  Clearly  the  occlusion  of  the  pyloric  orifice 
alone  would  account  for  Serdjukow's  results.  What  is  the  evidence  that 
peristalsis  also  was  affected  ? 


100          THE   MECHANICAL   FACTOKS    OF  DIGESTION 

remains,  has  been  presented  in  a  previous  chapter.  In  my 
experience,  neither  ejaculation  of  acid  chyme  nor  stretching  of 
the  duodenum  with  food  pressed  through  the  cut  pylorus  (see 
footnote,  p.  97)  has  any  tendency  to  interrupt  the  sequence  of 
waves.  As  remarked  in  the  discussion  of  mechanical  agencies 
acting  in  the  stomach,  the  waves  do  not  show  from  moment  to 
moment  marked  variation  of  intensity.  One  of  the  two  factors 
concerned  in  gastric  discharge — the  pressure  in  the  vestibule — 
is  therefore  recurrently  constant.  The  control  of  the  discharge, 
consequently,  must  reside  with  the  other  factor — i.e.,  with  the 
action  of  the  pyloric  sphincter.  If  the  sphincter  holds  tight,  the 
recurring  waves  churn  the  food  in  the  vestibule  ;  if  the  sphincter 
relaxes,  these  waves  press  the  food  out  into  the  duodenum.  The 
pylorus  is  the  "  keeper  of  the  gate." 

The  discharge  from  the  stomach,  as  we  now  know,  is  occasional. 
The  foregoing  analysis  proves  that  this  occasional  discharge  must 
be  due  to  occasional  relaxations  of  the  pyloric  sphincter.  To 
explain  the  action  of  the  pylorus,  therefore,  it  is  necessary  to 
consider  agencies  which  maintain  an  intermittent  closure — 
which  usually  keep  the  passage  shut,  yet  open  it  at  intervals  to 
allow  portions  of  the  chyme  to  depart.  None  of  the  researches 
on  the  control  of  gastric  evacuation,  discussed  in  the  preceding 
pages,  were  definitely  concerned  with  this  intermittent  closure. 
Further  investigation  was  desirable  to  explain  the  repeated 
opening  and  shutting  of  the  pyloric  orifice. 

Further  investigation  was  necessary  also  to  explain  the  striking 
differences  in  the  rate  of  discharge  of  different  foodstuffs. 
The  facts  presented  in  the  foregoing  chapter  immediately  raised 
the  question,  What  is  the  pyloric  mechanism  whereby  carbo- 
hydrates, not  digested  by  the  gastric  juice,  are  permitted  to  pass 
quickly  into  the  small  intestine  to  be  digested,  whereas  proteins, 
digested  in  the  stomach,  are  there  retained  to  undergo  digestion  ? 

As  we  have  learned,  investigators  have  hitherto  regarded 
factors  in  the  stomach,  or  factors  in  the  intestine,  as  controlling 
gastric  evacuation.  An  interaction  of  agencies  in  the  two 
situations  has  not  been  considered.  A  theory  based  on  evidence 
of  opposed  effects  from  a  single  stimulus  acting  first  in  the 
stomach  and  later  in  the  duodenum  I  propounded18  in  1904,  to 
explain  the  differential  discharge  of  the  different  foodstuffs. 

The  first  statement  in  the  theory  is  that  acid  coming  to  the 
pylorus  causes  a  relaxation  of  the  sphincter.  Thus  would  be 


THE  ACID  CONTROL  OF  THE  PYLORUS      101 

explained  why  the  initial  discharge  is  longer  delayed  when 
proteins  are  fed  than  when  carbohydrates  are  fed.  Both  carbo- 
hydrate and  protein  stimulate  gastric  secretion  in  abundance, 
as  researches  on  dogs  by  Pawlow  and  his  co-workers,19  and  as 
clinical  studies  on  men,  have  shown.  Inasmuch  as  carbo- 
hydrates do  not  unite  chemically  with  the  acid,  free  acid  is  at 
once  present  in  the  stomach ;  carbohydrates  would  therefore 
begin  almost  immediately  to  pass  through  the  pylorus.  Pro- 
teins, on  the  other  hand,  join  with  the  acid,  and  thus  retard  for 
some  time  the  development  of  an  acid  reaction  ;20  the  protein 
discharge  would  therefore  be  retarded. 

But  acid  on  the  stomach  side  of  the  pylorus  is  not  the 
only  determinant  of  pyloric  action.  The  observations  of  Hirsch 
and  Serdjukow  now  have  their  bearing.  Since  it  has  been  shown 
that  acid  in  the  duodenum  does  not  stop  gastric  peristalsis,  the 
acid  reflex  from  the  duodenum  must  affect  the  pyloric  sphincter. 
The  second  statement  in  the  theory  naturally  follows — acid  in 
the  duodenum  closes  the  pylorus. 

It  is  probable  that  the  pyloric  sphincter  has  normally  a  greater 
or  less  degree  of  tonic  contraction,  with  occasional  relaxations.21 
Certainly  it  has  a  tonic  contraction  persistently  strong  for  some 
time  after  food  enters  the  stomach.  When  protein,  for  example, 
is  fed,  peristaltic  constrictions  may  press  the  food  against  the 
pylorus  repeatedly  for  a  half-hour  or  more  (approximately,  150 
waves)  without  forcing  food  through  the  orifice. 

The  whole  theory  of  the  acid  control  of  the  pylorus  may  now 
be  stated.  The  pylorus  is  tonically  closed  when  food  is  ingested, 
and  remains  closed  against  recurring  pressure.  The  appearance  of 
acid  at  the  pylorus  causes  the  sphincter  to  relax.  The  pressing 
peristaltic  waves  now  force  some  of  the  acid  chyme  into  the 
duodenum.  The  acid  in  the  duodenum  at  once  tightens  the 
sphincter  against  further  exit.  The  same  acid  also  stimulates 
the  flow  of  alkaline  pancreatic  juice.22  Since  no  inorganic  acid 
is  normally  present  beyond  the  first  centimetres  of  the  small 
intestine,23  and  since  the  acid  reaction  of  the  contents  in  this 
uppermost  region  is  replaced  throughout  the  rest  of  the  small 
intestine  by  practically  a  neutral  reaction,24  the  acid  chyme 
must  be  neutralized  soon  after  its  emergence  from  the  stomach. 
As  neutralization  proceeds,  the  stimulus  closing  the  pylorus  is 
weakened ;  now  the  acid  in  the  stomach  is  able  again  to  relax 
the  sphincter.  Again  the  acid  food  goes  forth,  and  immediately 


102          THE   MECHANICAL   FACTORS    OF  DIGESTION 

closes  the  passage  behind  until  the  duodenal  processes  have 
undergone  their  slower  change.  And  thus,  repeatedly,  until 
the  stomach  is  empty.*  What  is  the  evidence  for  this  theory  ? 

As  the  acid  of  the  gastric  juice,  according  to  the  theory,  may 
have  two  opposing  effects  on  the  pylorus,  we  shall  review  first 
the  evidence  that  acid  in  the  vestibule  causes  the  pylorus  to 
open,  and  afterwards  the  evidence  that  acid  in  the  duodenum 
causes  the  pylorus  to  be  kept  closed. 

The  evidence  that  acid  in  the  vestibule  opens  the  pylorus  we 
shall  consider  under  several  headings,  as  follows  : 

1.  Delaying  the  appearance  of  hydrochloric  acid  delays  the 
initial  discharge.  In  terms  of  the  above  theory  the  quick  exit 
of  carbohydrates  is  due  to  the  early  appearance  of  acid  in  the 
stomach.  The  appearance  of  acid  can  be  delayed  if  the  carbo- 
hydrates are  first  moistened  with  sodium  bicarbonate.  Then  the 
acid  would  first  be  neutralized  by  the  alkaline  food  near  the 
secreting  surface  and  in  the  churning  vestibule  ;  and  only  after 
some  time  would  an  acid  reaction  appear  in  considerable  amount. 
If  the  theory  is  correct,  this  postponement  of  the  appearance  of 
acid  should  delay  beyond  the  normal  time  the  initial  discharge 
of  the  food. 

Crackers,  rice,  and  mashed  potatoes  were  chosen  as  repre- 
sentative carbohydrate  foods.  The  rice  was  steamed  and  dried, 
and  the  mashed  potato  was  also  dried  before  being  used.  In  all 
cases  1  per  cent,  sodium  bicarbonate  was  added  to  the  dried 
food  until  a  mush  was  made,  of  the  same  consistency  as  in  the 
standard  cases.  The  carbohydrates  thus  prepared  were  mixed 
with  subnitrate  of  bismuth,  and  fed,  as  in  the  standard  cases,  in 
25  c.c.  amounts.  The  average  figures  for  twelve  cases  in  which 
the  three  carbohydrates  wet  with  water  were  fed,  and  the  twelve 
cases  in  which  they  were  fed  wet  with  sodium  bicarbonate,  are 
represented  graphically  in  Fig.  12. 

The  curves  show  that  at  the  end  of  a  half-hour  there  had 
emerged  only  about  one-tenth  as  much  of  the  food  wet  with  the 
alkaline  solution  as  of  the  same  food  wet  with  water  (in  six  of 
the  twelve  cases  no  alkaline  food  had  left  the  stomach) ;  at  the 
end  of  an  hour,  from  a  third  to  a  half  as  much  ;  and  in  two  hours, 
from  about  a  half  to  five-sixths  as  much.  In  other  words, 

*  Cohnheim,  in  his  summary  of  the  factors  controlling  the  discharge  of  food 
from  the  stomach  (Nagel's  Handb.  d.  Physiol.  d.  Mensch.,  Braunschweig,  1907, 
ii.,  p.  564),  mentioned  the  theory  here  propounded,  but  stated  that  my  evidence 
for  it  was  not  convincing.  It  is  fair  to  note  that  at  that  time  the  evidence  in 
a  complete  and  detailed  form  had  not  been  presented. 


THE  ACID  CONTROL  OF  THE  PYLORUS 


103 


there  has  been  a  marked  retardation  in  the  discharge  of  carbo- 
hydrates wet  with  the  alkaline  solution.  This  result  is  in  har- 
mony with  the  observation  by  Jaworski  on  man,  that  alkalinity 
of  the  contents  delays  the  emptying  of  the  stomach.25 

Sodium  bicarbonate  delays  the  appearance  of  acid  in  two  ways  : 
it  checks  the  secretion  of  the  gastric  juice,26  and  for  a  time  it 
unites  with  the  acid  of  the  gastric  juice  as  rapidly  as  it  is  poured 
out.  The  evidence  here  presented  shows  that  experimental 
conditions  delaying  the  appearance  of  hydrochloric  acid  delay 
the  discharge  from  the  stomach. 

2.  Hastening  the  appearance  of  an  acid  reaction  hastens  the 
initial  discharge.  According  to  the  theory,  as  already  stated, 
the  slow  passage  of  proteins  from  the 
stomach  is  due  to  their  union  with  the 
acid  of  the  gastric  juice,  which  prevents 
the  rapid  development  of  a  marked  acid 
state. 

Evidence  as  to  this  supposition  may 
be  secured  by  feeding  protein  food  that 
has  previously  been  changed  to  acid 
protein.  Fibrin,  lean  beef,  and  fowl, 
freed  from  fat,  were  chosen  as  repre- 
sentative protein  foods.  They  were 
mixed  with  10  per  cent,  hydrochloric 
acid,  and  allowed  to  stand  until  changed 
to  acid  protein.  The  free  acid  was  dia- 
lyzed  away  until  test  showed  none  present. 
As  the  change  to  acid  protein  was  accom- 
panied by  swelling  of  the  original  sub- 
stance, the  standard  protein  content 
was  to  some  extent  preserved  by  feeding  the  acid  protein  in 
twice  the  usual  amount.  Doubling  the  amount  of  the  natural 
protein  notably  retards  the  outgo  from  the  stomach.27  If 
changing  the  natural  to  acid  protein  has  no  effect  on  the  outgo 
from  the  stomach,  doubling  the  amount  should  likewise  retard 
the  outgo — certainly  should  not  accelerate  it. 

Fibrin,  fowl,  and  lean  beef  were  fed  as  acid  proteins  in  50  c.c. 
amounts,  and  with  the  same  consistency  as  in  the  standard 
cases.  In  Fig.  13  are  presented  the  curves  for  the  average 
figures  of  the  twelve  cases  in  which  these  same  foods  were  given 
as  acid  proteins. 


Hours   '     1 
FIG.  12. 

The  continuous  line  i 
the  curve  after  feeding 
potato,  rice,  an< 


crackers  (four 
each)  moistened  with 
water,  and  the  dot-line 
the  same,  moistened 
with  1  per  cent. 
NaHC03. 


104 


THE   MECHANICAL   FACTORS    OF   DIGESTION 


The  curves  show  that  at  the  end  of  a  half-hour  the  stomach 
had  discharged  from  five  to  ten  times  as  much  acid  protein  as 
natural  protein ;  three  to  ten  times  as  much  at  the  end  of  an 
hour ;  and  in  two  hours  about  twice  as  much  acid  protein  as 
natural  protein.  Evidently  the  change  to  acid  protein  and  the 
feeding  in  increased  amount  resulted  not  in  slowing,  but  in 
remarkably  accelerating  the  exit  from  the  stomach.  According 
to  Moritz,  Tobler,  and  Lang,  protein  discharged  through  the 
pylorus  may  be  merely  acid  protein,  unaccompanied  by  free 
hydrochloric  acid.28  In  that  case  the  protein  given  in  these 
cases  is  ready  to  leave  the  stomach.  If  any  acid  is  secreted  upon 
it,  free  acid  is  at  once  present,  and  appears,  therefore,  earlier 
CTn  than  when  natural  protein  is  fed.  The 

evidence  here  given  indicates  that,  when 
experimental  conditions  hasten  the  appear- 
ance of  an  acid  reaction,  the  discharge 
from  the  stomach  is  correspondingly 
hastened. 

3.    The   appearance   of    acid   near    the 
pylorus  closely  precedes   the  initial   dis- 
charge.    Although    in    the    experimental 
conditions   already   described   the    emer- 
IG'  1  '  gence  of  food  from  the  stomach  occurred 

The   continuous  line   is  . »       .  ,  j-i  i 

the  curve  after  feeding  as  if  acid  were  present  to  open  the  pylorus, 
its  presence  has  only  been  inferred  ;  there 
has  been  no  demonstration  that  acid  was 
present  when  the  iirst  food  passed  into  the 
duodenum.  The  relation  between  the 
first  development  of  acid  and  the  first  exit  of  the  food  should 
be  more  exactly  determined.  This  can  be  done  by  establishing 
in  the  vestibule,  close  to  the  pylorus,  a  fistula. 

A  fistula  holding  a  simple  flanged  cannula  with  a  removable 
plug  was  established  in  the  vestibule  in  several  cats.  The  cats 
recovered  readily  from  the  operation,  and  were  usually  in  very 
good  health.  In  order  that  the  food  could  be  seen  with  the 
X  rays  when  it  first  entered  the  duodenum,  it  was  always  mixed 
with  bismuth  subnitrate.  When  potato  was  fed,  20  drops  of 
dimethylamidoazobenzol  were  added — an  amount  staining  the 
potato  orange,  and  showing  a  clearly  marked  change  to  pink 
when  hydrochloric  acid  developed.  As  soon  as  the  potato  was 
given  (usually  by  stomach-tube),  the  plug  was  removed  from 


10 


Hours 


fibrin,  fowl,  and  lean 
beef  (four  cases  each) 
as  natural  protein,  and 
the  dot-line  the  same, 
as  acid  protein. 


THE  ACID  CONTKOL  OF  THE  PYLOEUS      105 

the  cylinder  of  the  cannula,  and  replaced  by  a  tight-fitting  glass 
syringe.  By  pulling  up  the  piston  the  thin  mushy  contents  of 
the  vestibule  were  drawn  slightly  into  the  glass  tube.  Then  any 
change  of  colour  could  be  noted.  If  the  original  orange  colour 
still  persisted,  the  piston  was  pushed  down  again,  and  thus  the 
food  was  restored  normally  to  the  stomach.  Usually  such 
observations  were  made  every  four  minutes  ;  during  the  intervals 
X-ray  observations  showed  whether  food  had  yet  been  passed 
into  the  duodenum.  When  lean  beef  was  fed,  the  colour-change 
could  not  be  clearly  seen,  and  it  was  necessary  to  remove  through 
the  cannula  a  sample  of  the  vestibular  contents  in  a  small 
pipette.  The  contents  were  tested  for  acid  with  Congo-red, 
dimethylamidoazobenzol,  and  tropaolin  oo. 

Observations  through  the  fistula  proved  that  a  delay  in  the^ 
appearance  of  acid  in  the  contents  of  the  vestibule  is  associated 
with  a  similar  delay  in  the  passage  of  food  from  the  stomach  ; 
that  this  may  occur  in  spite  of  vigorous  gastric  peristalsis  ;  that 
under  these  circumstances  the  introduction  of  a  small  amount 
of  acid  near  the  pylorus  causes  immediately  the  exit  of  food 
through  the  pylorus  ;  and  that,  whether  potato  or  beef  is  fed,  and 
whether  in  the  same  animal  the  discharge  begins  at  the  usual 
time  or  is  much  retarded,  the  first  delivery  of  food  into  the 
duodenum  is  normally  preceded  by  the  development  of  an  acid 
reaction  in  the  vestibule. 

These  observations  on  the  vestibular  contents  are  well  sup- 
ported by  studies  of  the  reaction  of  the  discharged  chyme. 
Tobler,  London  and  Sulima,  and  London  and  Polowzowa,  have 
tested  the  chyme  collected  from  a  duodenal  fistula  close  to  the 
pylorus.  Tobler  fed  lean  beef  to  his  dogs.  The  repeatedly  dis- 
charged gastric  contents  were  acid  from  the  beginning,  and  con- 
tinued during  digestion  to  be  "stark  sauer."29  London  and 
Sulima30  recorded  that  when  cooked  egg-albumin  was  fed,  the 
discharge  from  the  pylorus  was  initiated  by  the  pouring  forth  of 
an  acid  fluid.  The  same  condition  was  recorded  by  London  and 
Polowzowa31  after  feeding  white  bread. 

4.  Hydrochloric  acid  opens  the  pylorus  of  the  excised  stomach. 
Magnus  has  shown32  that  pieces  of  the  small  intestine,  removed 
from  the  body  and  placed  in  warm,  oxygenated  Kinger's 
solution,  will  remain  alive  and,  so  long  as  the  myenteric  plexus 
is  intact,  will  manifest  the  typical  activities.  I  have  given 
evidence  that  the  mechanism  in  control  of  the  differential  dis- 


106          THE    MECHANICAL   FACTORS    OF   DIGESTION 

charge  through  the  pylorus  is  independent  of  the  central  nervous 
system.33  To  test  whether  the  mechanism  resides  in  the  local 
nerve  plexus,  the  following  experiment  was  performed  : 

A  cat  which  had  fasted  for  twenty-four  hours  was  quickly 
killed  by  etherization.  The  empty  stomach  was  removed  and 
placed  in  oxygenated  Ringer's  solution  (38°  C).  A  glass  tube, 
with  a  short  rubber  tube  and  a  water  manometer  attached,  was 
tied  into  the  cardiac  orifice.  A  small  amount  of  O4  per  cent. 
HC1,  made  blue  by  the  changed  Congo  red,  was  introduced  through 
the  tube  into  the  fundus,  which  was  held  lower  than  the  vestibule. 
The  stomach  was  now  inflated  until  air  bubbled  through  the 
pylorus.  The  rubber  tube  was  next  tightly  clamped.  When 
the  air  had  ceased  escaping — i.e.,  when  pyloric  tonus  withstood 
intragastric  pressure — the  stomach  was  gently  and  slowly  turned 
until  the  acid  came  to  the  pylorus.  In  a  moment  the  blue  fluid 
poured  forth  into  the  Ringer's  solution.  The  pylorus  had  opened. 

It  might  be  supposed  that  the  acid  coming  into  the  vestibule 
caused  an  increased  tonus  of  the  gastric  musculature,  and  that 
thus  the  pyloric  orifice  was  forced  open.  The  manometer,  how- 
ever, did  not  show  any  increase  of  intragastric  pressure.  Further- 
more, the  stomach  can  be  tipped  so  that  the  acid  fluid  enters 
the  vestibule,  but  does  not  come  to  the  pylorus.  This  did  not 
lead  to  the  driving  out  of  more  air ;  the  acid  did  not  notably 
stimulate  contraction  of  the  gastric  wall.  The  opening  of  the 
pylorus,  therefore,  was  due  to  the  presence  of  the  acid. 

A  1  per  cent,  sodium  bicarbonate  solution,  coloured  red, 
similarly  brought  to  the  pylorus,  did  not  begin  to  emerge  for  a 
considerably  longer  time,  and  then  usually  drifted  out  into  the 
Ringer's  solution  as  if  slowly  diffusing.  The  conclusion  is 
justified  that  in  the  living  excised  stomach  acid  coming  to  the 
pylorus  causes  the  pylorus  to  open. 

We  may  sum  up,  therefore,  as  follows,  the  evidence  that  acid 
on  the  stomach  side  of  the  pylorus  signals  the  relaxation  of  the 
sphincter.  Moistening  carbohydrates  with  NaHC03  retards  their 
normally  rapid  exit  from  the  stomach ;  feeding  proteins  as  acid 
proteins  remarkably  hastens  their  normally  slow  exit ;  observa- 
tions through  a  fistula  in  the  vestibule  show  that  an  acid  reaction 
closely  precedes  the  initial  passage  of  food  through  the  pylorus, 
that  the  introduction  of  acid  causes  pyloric  opening,  and  that 
delaying  the  acid  reaction  causes  retention  of  the  food  in  the 
stomach,  in  spite  of  strong  peristalsis ;  and,  when  the  stomach 


THE  ACID  CONTROL  OF  THE  PYLORUS      107 

is  excised  and  kept  alive  in  oxygenated  Ringer's  solution,  the 
pylorus  is  opened  by  acid  on  the  gastric  side.  What,  now,  is 
the  proof  that  acid  in  the  duodenum  keeps  the  pylorus  closed  ? 

The  support  for  the  second  half  of  the  theory,  that  acid  in 
the  duodenum  keeps  the  pylorus  closed,  has  already  been  in  part 
suggested.  As  other  observations  to  the  same  effect  are  to  be 
described,  however,  a  brief  restatement  of  the  experiments 
previously  mentioned  will  not  be  out  of  place,  and  will  serve  to 
bring  all  the  evidence  together. 

1.  Acid  in  the  duodenum  inhibits  gastric  discharge.  In  1893, 
Hirsch,  as  already  noted,  found  that  inorganic  acids  left  the 
stomach  slowly.  When  he  isolated  the  stomach,  however,  the 
acids  departed  as  rapidly  as  any  other  fluid.  He  explained  this 
difference  by  assuming  that  the  stomach  is  controlled  by  acid 
reflexes  from  the  duodenum.  Serdjukow  modified  Hirsch's 
experiment  by  introducing  through  a  duodenal  fistula  small 
quantities  of  acid  solutions  or  pure  gastric  juice.  By  repeated 
injections  it  was  possible  to  prevent  discharge  from  the  stomach 
for  an  unlimited  time.  Tobler's  observations  were  closer  to  the 
normal  conditions.  He  allowed  a  dog  with  duodenal  fistula  to 
eat  100  grammes  of  lean  beef.  The  chyme  as  it  emerged  was 
caused  to  leave  the  duodenum  through  the  artificial  opening. 
The  stomach  was  thus  emptied  in  about  two  hours  and  fifteen 
to  thirty  minutes.  The  next  day  the  dog  was  given  the  same 
amount  of  the  same  kind  of  food,  but  whenever  a  portion  of  the 
chyme  came  through  the  fistula  from  the  stomach,  a  similar 
portion  of  the  chyme  of  the  day  before  was  injected  through  the 
fistula  towards  the  intestines.  The  result  was  that  the  chyme 
left  the  stomach  at  considerably  longer  intervals,  and  was  more 
thoroughly  digested.  The  time  of  digestion  thus  became  length- 
ened to  three  hours  and  three  hours  and  a  half.  Tobler's 
observations  have  been  completely  confirmed  by  Lang.34 

The   experiments   of   Hirsch,  Serdjukow,  Tobler,  and  Lang 
prove  definitely  that  acid  chyme  in  the  duodenum  checks  the 
outgo  from  the  stomach.     Since  we  now  know  that  gastric 
peristalsis  is  not  stopped  by  the  discharge  of  acid  chyme,  the  . 
effect  must  be  due  to  the  action  on  the  pyloric  sphincter.     Acid  / 
in  the  duodenum  causes  pyloric  contraction. 

-2.  Absence  of  the  normal  alkaline  secretions  from  the  duo- 
denum retards  gastric  discharge.  Pawlow  has  recorded  that 
the  passage  of  acid  solutions  out  of  the  stomach  is  remarkably 


108 


THE   MECHANICAL   FACTOKS    OF   DIGESTION 


cm. 


30 


20 


10 


slower  in  dogs  with  a  pancreatic  fistula  than  in  those  without 
one.35  In  order  to  test  whether  the  discharge  of  normal  gastric 
contents  is  likewise  retarded  by  a  similar  condition  in  the 
duodenum,  the  following  experiment  was  performed :  The 
larger  pancreatic  duct  and  also  the  bile-duct  were  tied  so  as  to 
prevent  the  flow  of  the  secretions  into  the  intestine.  Six  and 
twelve  days  after  the  operation  the  animals  were  given  the 
standard  amount  of  mashed  potato  and  bismuth  subnitrate 
with  the  usual  consistency.  The  outgo  from  the  stomach  was 
determined,  as  before,  by  measuring  the  length  of  the  food- 
masses  in  the  small  intestine.  Fig.  14  presents  a  comparison 
of  the  discharge  under  normal  conditions 
and  after  tying  the  ducts.  Obviously  there 
has  been  a  very  marked  checking  of  the 
normal  rapid  outgo  of  the  potato  from  the 
stomach  ;  nothing  out  in  a  half-hour,  a 
fourth  the  normal  amount  in  an  hour,  and 
a  third  the  normal  at  the  end  of  two 
hours. 

Why  there  should  be  no  exit  of  the  food 
during  the  first  half-hour  is  not  clear,  but 
the  very  slow  increase  of  the  intestinal  con- 
tents thereafter — from  7 '5  to  14-5  centi- 
metres in  the  second  hour  of  digestion,  com- 
pared with  the  increase  from  10  to  31-5 
centimetres  in  the  second  half-hour  in  the 
normal  state — is  in  harmony  with  the  ob- 
servation that  acid  in  the  duodenum  closes 
the  pylorus. 

Under  normal  conditions,  acid  in  the  duodenum  stimulates 
the  secretion  of  pancreatic  juice  and  bile.  These  alkaline  fluids 
must  neutralize  the  acid  chyme,  for  an  acid  reaction  is  not  found 
beyond  the  first  few  centimetres  of  the  small  intestine  (see  p.  101). 
The  neutralizing  of  the  acid  removes  the  stimulus  keeping  the 
pylorus  closed.  If  the  alkaline  fluids  are  prevented  from  enter- 
ing the  intestine,  the  acid  is  necessarily  neutralized  more  slowly, 
the  pylorus  is  kept  closed  during  longer  periods,  and  the  emptying 
of  the  stomach  therefore  occurs  at  a  slower  rate. 

3.  Destroying  continuity  between  stomach  and  duodenum 
hastens  gastric  discharge.  Additional  evidence  as  to  the  rela- 
tions between  the  duodenum  and  the  pylorus  in  the  control  of 


Hours  i     1          2 
FIG.  14. 

The  continuous  line  is 
the  curve  after  feed- 
ing potato  (four  cases) 
in  normal  conditions, 
and  the  dot-line  the 
same,  with  pancreatic 
and  bile  ducts  tied.] 


THE  ACID  CONTROL  OF  THE  PYLORUS 


109 


cm. 


20 


10 


gastric  evacuation  can  be  secured  by  setting  aside  the  duodenum, 
and  causing  the  stomach  to  empty  into  a  lower  part  of  the  gut. 
The  intestine  was  cut  through  about  1-5  centimetres  beyond 
the  pyloric  furrow,  and  again  about  30  centimetres  beyond. 
The  upper  end  of  this  separated  portion  was  turned  in  and 
closed  with  stitches  ;  the  lower  end  was  joined  to  the  gut  near 
the  ileocolic  opening  by  an  end-to-side  junction.  The  upper  end 
of  the  main  part  of  the  intestine  was  now  united  to  the  small 
remnant  of  duodenum  contiguous  to  the  pylorus.  Thus  the 
stomach  emptied,  not  into  the  duodenum,  but  into  a  piece  of 
the  intestine,  formerly  30  centimetres  beyond. 

After  recovering  from  the  operation,  the  animals  were  fed 
shredded  lean  beef  of  standard  amount  and  consistency.  Kefer- 
ence  to  Fig.  15  shows  at  once  the  difference 
between  the  factor  which  acts  inside  the 
stomach  and  the  factor  which  acts  in  the 
duodenum  to  control  the  pylorus.  In  the 
normal,  and  in  the  experimental  conditions 
as  well,  there  occurred  the  retardation  of 
the  initial  discharge  characteristic  of  pro- 
teins. Setting  aside  the  duodenum  evi- 
dently did  not  change  that.  That  Hours  i  i  2 
retardation,  according  to  the  conclusions  FIG.  15. 

already  stated,  is  an  affair  of  the  stomach    Th^  continuous  line  is 

,  ,  . ,  , .  i  •      n  ,1          the  curve  after  feed- 

alone.     And  the  results  graphically  reported 

in  Fig.  15  serve  to  confirm  those  conclu- 
sions. 

When  the  food  begins  to  emerge,  the 
figures  are  suddenly  quite  different.  In- 
stead of  3  centimetres  at  the  end  of  an  hour,  16  centimetres  ; 
and  twice  the  normal  amount  at  the  end  of  two  hours — such  is 
the  effect  of  destroying  the  continuity  between  stomach  and 
duodenum.  After  the  first  delay  (in  one  case  no  food  left  the 
stomach  for  an  hour),  protein  is  poured  forth  at  a  remarkably 
rapid  rate. 

In  considering  agencies  affecting  the  cardia,  we  learned  that 
acid  in  the  stomach  increased  the  tonic  contraction  of  the 
sphincter  through  a  local  mechanism.  The  investigations  of 
Magnus  have  shown  that  intestinal  reflexes  occur  in  the  myen- 
teric  plexus.  It  seemed  probable  that  merely  cutting  a  ring 
around  the  intestine  as  close  as  possible  to  the  pylorus,  and 


ing  lean  beef  (four 
cases)  in  normal  con- 
ditions, and  the  dot- 
line  the  same,  with 
the  duodenum  set 
aside. 


110          THE   MECHANICAL   FACTORS    OF   DIGESTION 

deep  enough  to  sever  both  muscular  coats,  would  yield  informa- 
tion as  to  the  path  of  influence  from  duodenum  to  stomach.  A 
ring  was  cut  as  above  described,  and  the  separated  edges  of  the 
muscular  coats  were  then  held  together  by  only  the  mucosa  and 
the  submucous  connective  tissue.  When  protein  was  fed  there 
was  again  the  initial  delay — nothing  out  at  the  end  of  a  half- 
hour — and  this  was  followed  by  an  exit  almost  as  rapid  as  when 
the  duodenum  was  set  aside.  We  may  conclude  that  the  in- 
fluence from  duodenum  to  pylorus  runs  through  a  local  reflex, 
mediated  by  the  my  enteric  plexus.  In  the  intestinal  wall  is  a 
local  reflex,  such  that  a  stimulus  causes  a  contraction  above  the 
stimulated  point  and  a  relaxation  below.36  The  action  of  acid 
on  the  two  sides  of  the  pylorus  is  in  exact  agreement  with  this 
so-called  "  law  of  the  intestine  ";  the  acid  when  above  causes  a 
relaxation  of  the  sphincter  which  is  below,  and  the  acid  when 
below  causes  a  contraction  of  the  sphincter  which  is  above.  As 
we  have  already  seen,  the  cardia  also  obeys  this  law. 

We  may  sum  up,  as  follows,  the  evidence  that  acid  in  the 
duodenum  keeps  the  pylorus  closed.  Acid  in  the  duodenum 
inhibits  gastric  discharge,  as  proved  by  the  observations  of 
Hirsch,  Serdjukow,  and  Tobler — an  effect,  as  we  now  know,  not 
due  to  stoppage  of  peristalsis,  but  to  closure  of  the  pylorus  ;  the 
stomach  empties  more  slowly  than  normally  when  the  tying  of 
pancreatic  and  bile  ducts  prevents  alkaline  fluids  fromneutralizing 
the  acid  chyme  in  the  duodenum ;  the  discharge  of  protein 
becomes  rapid  if  the  pylorus  is  sutured  to  the  intestine  below  the 
duodenum,  or  if  a  ring  is  cut  through  the  muscular  coats  im- 
mediately beyond  the  pylorus.  The  effect  from  the  duodenum 
is  thus  a  local  reflex,  mediated,  like  the  local  reflex  of  the  small 
intestine,  by  the  myenteric  plexus. 

When  all  the  factors  concerned  in  the  proper  functioning  of  the 
pyloric  sphincter  are  considered,  the  simple  control  of  its  activity 
by  the  action  of  acid  above  and  below  must  be  regarded  as  one 
of  the  most  remarkable  automatisms  in  the  body.  The  highly 
important  part  which  the  pylorus  plays  seems  to  have  been 
surmised  by  the  ancients  who  gave  it  the  name,  "  keeper  of  the 
gate,"  and  called  it  also  "  rector  "  and  "  janitor  Justus."  How 
it  makes  the  relations  between  gastric  and  intestinal  digestive 
processes  orderly  and  progressive,  we  shall  next  consider. 


THE   ACID    CONTROL   OF  THE    PYLORUS  111 


REFERENCES. 

1  Ewald  and  Boas,  Arch.  f.  pcith.  Anat.,  1885,  ci.,  p.  365. 

2  Schiff,  Physiologic  de  la  Digestion,  Florence  and  Turin,  1867,  ii.,  p.  326; 
Kiihne,  Lehrb.  d.  physiol.  Chem.,  Leipzig,  1868,  p.  53  ;  also  v.  Mering,  Verhandl. 
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3  Richet,  Compt.  rend.  Acad.  d.  Sc.,  Paris,  1877,  Ixxxiv.,  p.  451  ;  Rossbach, 
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4  Cannon,  Am.  J.  Physiol.,  1898,  i.,  pp.  368,  369. 

5  Hirsch,  Centralbl.  f.  klin.  Med.,  1892,  xiii.,  p.  994. 

6  See  Lesshaft,  Arch.  f.  path.  Anat.,  1882,  Ixxxvii.,  p.  80. 

7  v.  Mering,  loc.  cit.,  p.  434. 

8  Marbaix,  La  Cellule,  1898,  xiv.,  p.  251. 

9  Tobler,  Ztschr.  f.  physiol.  Chem.,  1905,  xlv.,  p.  195. 

10  Cannon,  Am.  J.  Physiol.,  1902,  vi.,  p.  262. 

11  Ewald  and  Boas,  loc.  cit.,  p.  364. 

12  Penzoldt,  Deutsches  Arch.  f.  klin.  Med.,  1893, 1L,  p.  535  ;  1894,  liii.,  p.  230. 

13  Verhaegen,  La  Cellule,  1897,  xii.,  p.  69. 

4  Hirsch,  Centralbl.  /.  klin.  Med.,  1893,  xiv.,  p.  383. 

15  Serdjukow,  Abstract  in  Jahresb.  ii.  d.  Fortschr.  d.  Physiol.,  1899,  viii., 
p  .214. 

16  Tobler,  loc.  cit.,  p.  198. 

17  Marbaix,  loc.  cit.,  p.  273. 

18  Cannon,  Am.  J.  Physiol.,  1904,  x.,  p.  xviii. 

19  Pawlow,  loc.  cit.,  pp.  36,  100. 

20  Danilewsky,  Ztschr.  f.  physiol.  Chem.,  1881,  v.,  p.  160. 

21  See  Bastianelli,  Untersuch.  z.  Naturl.  d.  Mensch.  u.  d.  Thiere,  1892,  xiv., 
p.  93  ;  and  Oser,  Ztechr.  f.  klin.  Med.,  1892,  xx.,  p.  291. 

22  Bayliss  and  Starling,  Centralbl.  f.  Physiol.,  1901,  xv.,  p.  682. 

23  Moore  and  Bergin,  Am.  J.  Physiol.,  1900,  iii.,  p.  325. 
2*  Munk,  Centralbl.  f.  Physiol.,  1902,  xvi.,  p.  33. 

25  Jaworski,  Ztschr.  f.  BioL,  1883,  xix.,  p.  444. 
28  Pawlow,  loc.  cit.,  p.  95. 

27  See  Cannon,  Am.  J.  Physiol.,  1904,  xii.,  p.  409. 

28  Moritz,  Ztschr.  /.  BioL,  1901,  xlii.,  p.  571  ;  Tobler,  loc.  cit.,  p.  197  ;  Lang, 
Biochem.  Ztschr.,  1906,  ii.,  p.  240. 

29  Tobler,  loc.  cit.,  p.  197. 

30  London  and  Sulima,  Ztschr.  f.  physiol.  Chem.,  1905,  xlvi.,  p.  215. 

31  London  and  Polowzowa,  Ztschr.  f.  physiol.  Chem.,  1906,  xlix.,  p.  340. 

32  Magnus,  Arch.  f.  d.  ges.  Physiol.,  1904,  cii.,  p.  362. 

33  Cannon,  Am.  J.  Physiol.,  1906,  xvii.,  p.  429. 
3*  Lang,  loc,  cit.,  p.  225. 

35  Pawlow,  loc.  cit.,  p.  164. 

36  See  Bayliss  and  Starling,  J.  Physiol.,  1899,  xxiv.,  p.  142. 


CHAPTER  X 

THE  CORRELATING  FUNCTIONS  OF  THE  PYLORUS,  AND  SOME 
CONDITIONS  AFFECTING  IT 

THE  great  importance  of  the  pylorus  in  correlating  the  digestive 
processes  of  the  stomach  and  small  intestine  is  perhaps  brought 
out  most  impressively  if  we  consider  what  would  happen  if  the 
sphincter  did  not  perform  its  proper  functions.  Let  us  suppose 
that  it  opened  as  soon  as  gastric  peristalsis  started. 

We  know  from  Edkins's  experiments  that  gastric  juice  con- 
tinues to  be  secreted  because  acid,  peptone,  or  sugar  solutions 
affect  the  mucosa  of  the  vestibule.  Evidently,  if  the  pylorus 
opened  as  soon  as  the  peristaltic  waves  started,  they  would 
act  merely  to  propel  the  gastric  contents  rapidly  through  the 
stomach.  The  food,  therefore,  would  not  have  time  to  receive 
much  of  the  acid  secretion  of  the  cardiac  end,  nor  would  even 
the  small  amount  of  acid  that  the  food  might  carry  be  churned 
against  the  mucosa  of  the  vestibule.  That  the  processes  in  the 
stomach  may  advance  in  an  orderly  manner,  therefore,  the 
gastric  contents  must  be  retained  until  the  portion  in  the  vesti- 
bule is  churned  to  an  acid  chyme. 

Again,  if  the  food  were  allowed  to  depart  before  becoming 
acid,*  it  could  not  stimulate  chemically  the  duodenal  reflex. 
The  pylorus,  consequently,  would  not  be  held  closed,  and  the 
upper  small  intestine  would  be  crowded  full  of  food  through  an 
uncontrolled  pyloric  sphincter.  Furthermore,  the  chyme,  unless 
held  back  until  acid,  would  not,  on  entering  the  duodenum,  excite 
the  flow  of  pancreatic  juice  and  bile.  Thus,  if  the  pylorus 
relaxed  at  the  approach  of  the  first  peristaltic  wave  (after  meat 
had  been  fed,  for  example),  the  food  would  not  only  emerge 
wholly  undigested  by  gastric  juice,  but  would  bear  no  provision 
for  being  digested  by  the  pancreatic  juice.  In  order  that  the 

*  The  somewhat  variant  case  of  the  fats  will  be  considered  later. 
112 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS       113 

pancreatic  juice  may  be  caused  to  flow,  and  may  have  time  to 
become  mixed  thoroughly  with  the  chyme,  without  being  over- 
whelmed by  fresh  discharges  from  the  stomach,  food  must  be 
retained  in  the  vestibule  until  acid  in  reaction. 

If  we  grant  that  the  vestibular  contents  must  be  acid  before 
being  permitted  to  pass  the  pylorus,  note  how  favourably  the 
stomach  is  arranged  for  the  utilization  of  its  secretions.  We 
have  already  learned  that  in  order  to  open  the  sphincter  the 
acid  must  be  at  the  pylorus.  Clearly,  if  the  vestibule  secreted 
acid,  the  acid  would  at  once  open  the  pylorus  and  let  out  the 
food  (meat,  for  example)  before  the  gastric  juice  had  had  oppor- 
tunity to  digest  it.  But  the  vestibule  does  not  itself  secrete 
acid.  The  acid  and  the  food  with  an  acid  reaction  must  be 
brought  from  the  cardiac  end  of  the  stomach  and  thoroughly 
mixed  with  the  contents  of  the  vestibule  before  the  pylorus 
relaxes.  The  necessity  of  importing  the  acid  into  the  vestibule 
insures  a  thorough  mixing  of  the  food  with  the  gastric  juice 
before  the  food  departs,  and  provides  time  for  gastric  digestion. 

We  can  now  appreciate  how  wonderful  an  arrangement  the  acid 
control  of  the  pylorus  is— an  arrangement  whereby  the  food  is 
held  in  the  stomach  until  provision  is  made  for  the  continuance 
of  gastric  secretion,  until  the  gastric  juice  has  had  time  to  act, 
and  until  the  food  can  bear  with  it  the  acid  needed  for  processes 
in  the  duodenum.  In  the  duodenum  the  acid  chyme  stimulates 
the  flow  of  pancreatic  juice  and  bile,  and  holds  the  pylorus  closed 
until  this  chyme  has  been  thoroughly  mixed  with  these  digestive 
fluids.  This  thorough  mixing  stops  gastric  digestion,  injurious 
to  the  action  of  the  pancreatic  ferments,  by  neutralizing  the 
acid.  As  the  acid  is  neutralized,  the  stimulus  holding  the  pylorus 
closed  is  weakened,  and  then  the  acid  in  the  stomach  is  again 
effective  in  causing  the  pylorus  to  open. 

We  shall  find  still  more  reason  for  admiration  of  the  pyloric 
reflex  when  we  see  how  exactly  its  acid  control  can  be  applied 
in  explaining  the  differential  discharge  of  different  foodstuffs. 
The  delay  in  the  initial  discharge  of  protein  food  we  have  already 
explained  as  due  to  the  union  of  the  first  acid  secreted  with  the 
protein.  The  continued  slow  exit  can  also  be  explained.  The 
mixing  occurs  only  in  the  pyloric  end  ;  as  we  know,  the  centre 
of  the  mass  in  the  cardiac  end  long  remains  unchanged  in  reaction. 
Since  the  vestibule  does  not  secrete  acid,  all  the  acidity  of  its 
contents  is  due  to  acid  pressed  in  from  the  cardiac  end.  But 

8 


114          THE   MECHANICAL   FACTORS    OF   DIGESTION 

unchanged  protein,  stored  in  the  cardiac  end,  is  also  continuously 
being  pressed  into  the  vestibule.  There  is  thus  continuous 
utilization  of  the  imported  acid.  Since  it  is  altogether  probable 
that  a  certain  degree  of  acidity  is  necessary  for  opening  the 
pylorus,  the  fresh  protein  masses,  by  uniting  with  the  acid  and 
thus  reducing  the  acid  reaction,  would  naturally  diminish  the 
rate  of  exit  from  the  stomach.  That  this  factor  is  important 
in  checking  the  rapid  outgo  of  protein  food  is  indicated  by 
the  quick  discharge  of  acid  proteins,  which  do  not  demand  large 
amounts  of  acid  (cf.  two  curves  in  Fig.  15).  Possibly  also  the 
protein  discharge  continues  to  be  slow  because  protein  chyme 
presents  a  greater  amount  of  acid  for  neutralization  than  does 
carbohydrate  chyme.  Tobler  and  Lang  have  shown  that  acid 
protein  in  the  duodenum  will  check  gastric  evacuation.1 
Khigine's  results  prove  that,  when  200  grammes  of  flesh  are  fed  to 
a  dog,  50  per  cent,  more  gastric  juice  is  secreted  during  the  first 
four  hours  of  digestion  than  is  secreted  in  the  same  time  when  the 
same  amount  of  bread  is  fed.2  The  neutralizing  of  the  larger 
amount  of  acid  in  the  duodenum  would  naturally  require  a 
longer  time,  and  would  result  in  a  slower  rate  of  discharge  than 
would  be  expected  when  bread  is  fed. 

In  examining  the  effects  of  feeding  combinations  of  foodstuffs, 
we  noted  that  when  carbohydrate  was  fed  first,  and  protein 
second,  the  departure  of  the  carbohydrate  was  not  materially 
checked  ;  but  that  when  protein  was  fed  first,  and  carbohydrate 
second,  the  protein  held  back  the  carbohydrate.  In  the  former 
case  the  carbohydrate  content  of  the  vestibule  did  not  retard 
the  development  there  of  an  acid  reaction  ;  in  the  latter  case  the 
protein  did  retard  that  development.  This  observation  indi- 
cates that  the  acid  which  opens  the  pylorus  acts  close  to  the 
pylorus — a  conclusion  which  is  sustained  by  the  -effect  of  acid 
in  the  excised  stomach. 

When  carbohydrates  and  proteins  were  mixed  in  equal  parts, 
the  discharge  was  intermediate  in  rapidity.  This  result  is  in 
accord  with  other  evidence,  for  a  large  proportion  of  protein 
was  present  to  unite  with  the  acid  secreted,  and  this  would  tend 
to  retard  the  discharge  in  the  usual  manner. 

In  a  mixture  of  fats  and  proteins  in  equal  parts,  the  presence 
of  fat  caused  the  mixture  to  leave  the  stomach  even  more  slowly 
than  the  protein  alone.  This  result  also  is  in  accord  with  the 
supposition  that  acid  opens  the  pylorus,  for  fat  alone  inhibits? 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS       115 

and  fat  mixed  with  protein  notably  retards  and  diminishes,  the 
flow  of  gastric  juice.3  Moreover,  the  development  of  an  acid 
reaction  is  checked  by  the  union  of  acid  with  protein.  Quite 
naturally,  therefore,  this  combination  of  foodstuffs  was  slowest 
of  all  to  pass  from  the  stomach.* 

Fats  mixed  with  carbohydrates  in  equal  amounts  caused  the 
carbohydrates  to  pass  the  pylorus  at  a  rate  slower  than  their 
normal.  In  this  case  the  fats  again  retarded  and  diminished 
secretion  ;  but  the  carbohydrates,  unlike  the  proteins,  did  not 
further  hinder  the  appearance  of  an  acid  reaction.  The  checking 
of  the  outgo  can  therefore  be  explained  by  the  effect  of  the  fats 
in  diminishing  gastric  secretion. 

The  evidence  just  presented  indicates  that  typical  variations 
in  the  rate  of  discharge  of  proteins,  carbohydrates,  and  fats, 
and  combinations  of  these  foodstuffs,  can  be  readily  explained 
by  the  action  of  acid  upon  the  pylorus.  This  ability  to  explain 
the  peculiar  differences  in  the  gastric  discharge  of  the  different 
foodstuffs  brings  additional  strength  to  the  evidence  already 
given  that  acid  acting  oppositely  above  and  below  controls  the 
pyloric  passage. 

The  discharge  of  fats  is  peculiar,  and  requires  special  con- 
sideration. In  attempting  to  understand  their  prolonged  slow 
discharge,  we  must  first  consider  their  effects  both  in  the  stomach 
and  in  the  duodenum.  We  know  that  fat  in  the  stomach  does 
not  stimulate  the  flow  of  gastric  juice.  On  the  other  hand, 
according  to  Lintwarew,4  fat  in  the  duodenum,  like  acid,  may 
check  the  gastric  discharge. 

Associated  with  the  absence  of  gastric  secretion  there  is 
apparently  a  low  degree  of  pyloric  tonus.  Boldireff,  for  example. 
has  reported  that,  when  fats  are  fed  in  considerable  amount,  a 
mixture  of  pancreatic  juice,  bile,  and  intestinal  secretion,  flows 
back  into  the  stomach.6  This  result  could  not  occur  unless  at 
times  the  pyloric  sphincter  were  in  a  relaxed  state,  and  unless  at 

*  An  important  food  consisting  of  a  combination  of  fat  and  protein  is  milk. 
Before  being  coagulated,  milk  issues  from  the  stomach  in  gushes,  like  water, 
as  we  shall  see  later.  Clearly,  were  not  milk  quickly  coagulated,  it  would  go 
at  once  into  the  intestine,  unchanged  and  not  provided  with  acid  to  help  rouse 


pancreatic   secretion.     Once  coagulated,  however,   milk  leaves  the  stomach 

.,  1901,  xlii.,  p. 
d.  Gesdlsch.  /.  Kinderheilk.,  1906,  p.   147),  the  chyme  from  milk  is  a  clear 


slowly  (Moritz,  Ztschr.  /.  Bid.,  1901,  xlii.,  p.  575).     According  to  Tobler  (Verh. 


yellowish  fluid,  with  the  protein  mostly  changed  to  peptone.  Coagulation 
may  be  interpreted,  therefore,  as  a  conservative  provision  delaying  the  passage 
from  the  stomach  until  peptonization  has  occurred.  The  slow  discharge  of  a 
fat-rich  milk,  after  the  first  few  gushes  through  the  pylorus,  can  be  explained 
by  the  combination  of  fat  and  protein  in  its  composition. 


116          THE   MECHANICAL   FACTORS    OF   DIGESTION 

times  the  pressure  in  the  stomach  were  less  than  that  in  the 
duodenum.  In  this  connection  it  is  of  interest  to  recall  that, 
of  the  three  foodstuffs,  fats  produce  the  slowest  rate  of  gastric 
peristalsis  (see  p.  55),  and  commonly  the  weakest  (i.e.,  the 
shallowest)  waves.  My  observations  do  not  support  Cohnheim's 
suggestion6  that  fat  in  the  duodenum  stops  gastric  peristalsis. 

Fats  differ  from  carbohydrates  and  proteins  in  very  seldom 
constituting  the  chief  elements  of  a  diet.  They  differ  also  in 
npj^arousing  gastric  secretion.  They  are  further  peculiar  in 
acting  by  themselves  in  the  duodenum,  not  only  to  inhibit  gastric 
evacuation,  but  also  to  stimulate  the  flow  of  pancreatic  juice.7 
Clearly,  fats  do  not  require  the  secretion  of  gastric  juice  for 
changes  in  the  stomach,  or  for  the  control  of  their  exit  into  the 
intestine,  or  for  the  stimulation  of  a  pancreatic  secretion  specially 
favourable  to  their  digestion. 

Although  fats  have  a  special  relation  to  the  pyloric  mechanism, 
the  alternative  possibility  of  an  acid  control,  even  when  fats 
alone  are  fed,  should  not  be  overlooked.  Fatty  acid  may  be 
set  free  in  considerable  amount  in  the  stomach  by  gastric  lipase 
if  the  fat  is  fed  as  an  emulsion.8  A  separation  of  fatty  acid  also 
occurs  when,  in  the  early  stages  of  fat  digestion,  pancreatic  juice 
enters  the  stomach.9  If,  at  first,  fats  readily  pass  through  an 
easily  opened  pylorus,  the  later  development  of  acid  in  fats  in 
the  stomach  might  cause  them  to  control  their  own  discharge,  like 
other  foods  which  develop  an  acid  reaction  of  the  gastric  contents. 
And  in  the  duodenum  it  is  noteworthy  that  fats  are  changed 
with  an  effect  quite  unlike  that  of  the  other  foodstuffs.  Fats 
cause  the  pancreatic  juice  to  flow,  but  the  pancreatic  juice, 
instead  of  diminishing  the  acidity  of  the  duodenal  contents, 
increases  the  acidity  by  separating  a  still  greater  amount  of 
fatty  acid.10  Even  when  dissolved  in  bile,  the  fatty  acids  give 
the  solution  an  acid  reaction.11  To  this  increasing  acidity  of  the 
contents  of  the  upper  intestine,  as  well  as  to  the  action  of  fats 
themselves,  and  the  weak  and  sluggish  gastric  peristalsis  which 
they  evoke,  may  reasonably  be  attributed  the  fact  that  fats  pass 
from  the  stomach  only  as  fast  as  they  are  absorbed  or  carried 
into  the  large  intestine. 

The  low  pyloric  tonus  and  the  inhibition  of  gastric  secretion 
— conditions  which  attend  the  ingestion  of  fat — are  possibly 
related  through  the  action  of  the  vagus  nerves.  Pawlow  has 
shown  that  the  psychic  secretion  of  gastric  juice  is  due  to  im- 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS        117 

pulses  coming  to  the  stomach  by  way  of  the  vagi.12  Vagus 
stimulation  also  produces  an  augmentation  of  the  contraction 
of  the  pyloric  sphincter.13  Vagus  impulses,  therefore,  cause  the 
initial  flow  of  gastric  juice — the  psychic  secretion — and  they  also 
cause  increased  pyloric  tonus.  In  the  absence  of  one  effect  of 
vagus  stimulation,  we  might  find  the  other  effect  also  lacking. 
Certainly  that  seems  to  be  true  for  the  fats.  It  is  also  a  possible 
explanation  of  several  other  conditions  of  anomalous  discharge 
from  the  stomach — among  them,  the  discharge  of  water  and 
egg-white. 

Water  begins  to  enter  the  intestine  almost  as  soon  as  it  enters 
the  stomach  ;  it  may  pass  out  in  single  gushes  or  continuously. 
According  to  Moritz,  who  watched  the  process  through  a  duo- 
denal fistula,  500  c.c.  of  water  may  go  from  the  stomach  into 
the  intestine  in  thirty  minutes.14  Similar  results  have  also  been 
reported  by  other  observers  who  have  studied  the  exit  of 
water.15  Physiological  salt  solution  likewise  may  go  out 
rapidly.16 

Water  and  salt  solution  are,  of  course,  very  different  in  con- 
sistency from  the  foods  ordinarily  taken  into  the  stomach. 
Furthermore,  water  and  salt  solution  neither  present  the  con- 
ditions for  psychic  secretion  (they  are  not  chewed  with  a  relish, 
they  are  swallowed  rapidly,  they  do  not  satisfy  appetite),  nor, 
once  in  the  stomach,  do  they  produce  any  considerable  secretion 
of  gastric  juice.  When  only  100  or  150  c.c.  of  water  are  injected, 
very  often  not  the  least  trace  of  secretion  occurs.  "  It  is  only  a 
prolonged  and  widely-spread  contact  of  the  water  with  the 
gastric  mucous  membrane  which  gives  a  constant  and  positive 
result  (secretion)."17  The  rapid  exit  of  water  from  the  stomach 
would  preclude  the  conditions  which  make  it  even  a  feeble 
stimulant  of  gastric  secretion.  And  the  failure  of  water  to  excite 
any  noteworthy  amount  of  gastric  juice  favours  a  rapid  exit,  so 
far  as  the  duodenal  reflex  is  concerned,  for  the  acid  stimulus 
closing  the  pylorus  is  thereby  absent.  Within  the  stomach, 
water  certainly  has  an  effect  on  the  pyloric  sphincter  very  dif- 
ferent from  foods  which  evoke  an  abundant  flow  of  gastric  juice. 
When  such  foods  are  given,  scores  of  peristaltic  waves  may 
sweep  up  to  the  pylorus  before  the  sphincter  relaxes  ;  but  when 
water  is  given,  it  begins  to  leave  the  stomach  at  once.*  The 

*  The  quick  exit  of  water,  before  it  is  acidified,  doubtless  explains  the 
readiness  with  which  it  conveys  infection. 


118          THE   MECHANICAL   FACTORS    OF   DIGESTION 

fact  that  water  may  pour  through  the  pylorus  in  a  fairly  con- 
tinuous stream,  as  rapidly  as  it  is  swallowed,  points  definitely 
to  a  diminished  pyloric  tonus.  This  fact  and  the  failure  to 
stimulate  gastric  secretion  are,  as  I  have  pointed  out,  apparently 
related  to  each  other.  In  these  facts  may  be  found  a 
probable  explanation  of  the  rapid  discharge  of  water  from  the 
stomach.* 

In  the  same  class  with  water  is  raw  egg-white.  In  my  observa- 
tions on  the  rate  of  discharge  of  different  foods  from  the  stomach, 
I  pointed  out  that  egg-albumin  formed  an  exception  to  the 
general  rule  that  protein  passes  out  from  the  stomach  slowly.18 
This  observation  is  confirmed  by  London  and  Sulima's  study  of 
dogs  with  a  duodenal  fistula.  They  found  that  raw  egg-albumin 
begins  to  pass  the  pylorus  immediately  after  ingestion ;  it 
emerges  in  large  gushes  at  intervals  of  four  or  five  seconds. 
These  gushes  are  therefore  too  frequent  to  correspond  to  the 
occurrence  of  peristaltic  waves.  For  about  twenty  minutes  the 
egg-white  issues  from  the  stomach  with  an  alkaline  reaction  ; 
then  the  reaction  becomes  acid,  and  the  discharge  naturally  is 
more  seldom  (one  to  three  minute  intervals)  and  less  abundant.19 
In  this  connection  it  is  of  interest  that  Pawlow  found  fluid  egg- 
white  no  more  effective  in  exciting  gastric  secretion  than  an  equal 
volume  of  water.20  Like  water, fluid  egg-white  does  not  offer  the 
conditions  for  arousing  psychic  secretion  ;  and  again,  attending 
that  condition,  there  is  a  state  of  diminished  pyloric  tonus,  as 
evidenced  by  discharges  through  the  pylorus  much  more  frequent 
than  the  peristaltic  waves  in  the  dog's  stomach.  The  rapid 
passage  of  fluid  egg-white  from  the  stomach  would  therefore  be 

*  Cohnheim  states  that  water  swallowed  by  dogs  when  the  stomach  is  full 
passes  along  the  lesser  curvature,  through  a  little  channel  formed  there,  and, 
diluting  only  the  contents  of  the  vestibule,  pours  through  the  pylorus.  After 
the  first  few  gushes  the  water  appears  at  the  duodenal  fistula,  free  from  gastric 
contents,  and  almost  neutral  in  reaction  (Mi'mchen.  med.  Wchnschr.,  1907,  liv., 
p.  2582).  I  have  some  tracings  made  in  1898,  showing  how  water  containing 
bismuth,  when  swallowed  into  a  full  stomach,  leaves  the  bismuth  lying  along 
the  lesser  curvature.  It  occurred  to  me  then  that  this  phenomenon  in  a  car- 
nivorous animal  was  not  unlike  the  course  of  the  more  fluid  food  in  ruminants  ; 
but  as  I  had  no  further  evidence,  I  did  not  call  attention  to  the  observation. 
The  strong,  oblique  fibres  of  the  inner  muscular  coat  (see  p.  47)  would  help 
to  make  a  channel  by  their  contraction.  There  is  not,  however,  entire  agree- 
ment among  observers  on  the  passage  of  water  through  the  stomach  during 
gastric  digestion.  Leven  and  Barret  have  found  that,  whereas  water  dis- 
appears rapidly  from  the  resting  stomach,  its  discharge  is  considerably  retarded 
if  taken  with  food,  even  with  a  few  bites  of  bread  (Radioscopie  Gastrique  et 
Maladies  de  VEstomac,  Paris,  1909,  p.  75).  Of  course,  the  delay* under  these 
circumstances  is  readily  explained. 


COEEELATING   FUNCTIONS    OF  THE   PYLOEUS        119 

explained  in  the  same  manner  that  the  rapid  outgo  of  water  is 
explained.* 

According  to  my  earlier  investigations,  egg-white  coagulated 
by  heat  also  left  the  stomach  at  a  rapid  rate.  This  observation, 
likewise,  is  confirmed  by  London  and  Sulima.  They  found, 
however,  that,  unlike  fluid  egg-white,  the  coagulated  form  did 
not  begin  to  leave  the  stomach  immediately,  but  several  minutes 
after  ingestion.  When  the  gastric  discharge  began,  its  reaction 
was  acid.  First  the  discharge  had  only  fine  particles  of  the  egg- 
albumin,  but  later  these  were  much  larger.21  These  unchanged 
particles  are  significant,  for  they  indicate  that  the  acid  has  been 
secreted  more  rapidly  than  it  could  unite  with  the  compact 
coagulum  of  the  egg-albumin.22  This  failure  of  the  acid  to  unite 
with  albumin  as  soon  as  secreted  brings  about  the  same  condition 
that  prevails  when  carbohydrates  are  fed :  there  is  an  early 
appearance  of  free  acid  in  the  stomach.  London  and  Sulima 
reported  large  amounts  of  free  hydrochloric  acid  in  the  chyme  of 
coagulated  egg-white.23  On  the  other  hand,  although  the  chyme 
of  beef  and  fibrin  is  acid  in  reaction,  it  may  not  contain  free 
hydrochloric  acid  (see  p.  104).  This  difference  in  the  rapidity  of 
union  with  the  acid  as  it  is  secreted  would  account  for  the  differ- 
ence in  the  rate  of  discharge  of  these  proteins.  The  slow  union  of 
acid  with  coagulated  egg-white,  and  the  resultant  early  appear- 
ance of  free  acid  in  the  stomach,  explains  the  rapid  departure  of 
this  food. 

That  water  does  not  emerge  rapidly  from  the  stomach  merely 
because  it  is  fluid  was  shown  by  the  observations  of  Moritz.24 
Weak  hydrochloric  acid,  he  found,  passed  out  more  slowly  than 
water,  and  beer  passed  out  with  even  greater  retardation.  The 
slow  exit  of  weak  hydrochloric  acid  can  be  explained  by  its  effect 
in  closing  the  pylorus  from  the  duodenal  side.  And  beer,  stimu- 
lating gastric  secretion  not  only  by  its  alcohol  content,25  but  also 
by  its  bitter  taste, ^6  must  go  out  slowly,  because  of  the  acid  con- 
trol of  the  pyloric  passage. 

In  connection  with  the  acid  control  of  the  pylorus  the  effect  of 
hyperacidity  may  be  considered.  By  requiring  a  longer  time  for 
neutralization  in  the  duodenum,  and  thereby  holding  the  pylorus 
closed  for  longer  periods,  hyperacidity  might  be  expected  to  cause 
a  retardation  of  gastric  discharge.  In  work  with  C.  A.  Hedblom, 

*  A  very  rapid  exit  of  a  rice  preparation  moistened  with  sodium  bicarbonate 
(which  hinders  gastric  secretion)  may  be  similarly  explained. 


120          THE  MECHANICAL  FACTORS    OF  DIGESTION 


evidence  on  this  question  was  obtained  by  feeding  potato  with 
which  had  been  mixed  a  known  percentage  of  hydrochloric  acid. 
The  results  are  represented  in  the  curves  of  Fig.  16. 

In  comparing  with  the  standard  rate  the  results  of  feeding  acid 
food,  it  is  fairer  to  use  the  second  rather  than  the  first  half-hour 
of  the  standard  curve,  since  at  the  beginning  of  the  first  half-hour 
digestion  has  not  begun  and  no  acid  has  yet  appeared  at  the 
pylorus,  while  at  the  beginning  of  the  second  half-hour  acid  chyme 
is  being  discharged.  As  the  curves  indicate,  the  rate  of  exit  is 
faster  than  normal  when  the  potato  has  an 
acidity  of  0-25  per  cent.,  and  slower  than 
normal  when  it  has  an  acidity  of  1  per  cent. 
Potato  with  an  acidity  of  0-5  per  cent,  is 
discharged  during  the  first  half-hour  about 
as  rapidly  as  the  food  is  normally  dis- 
charged. The  difference  between  the  outgo 
of  the  weakly  acid  (0-25  per  cent.)  and  the 
strongly  acid  (1  per  cent.)  potato  is  re- 
markable. Note  that  at  the  end  of  the 
first  half-hour  there  was  in  the  intestine 
more  than  2-5  times  as  much,  and  at  the 
end  of  an  hour  about  two  times  as  much, 
of  the  weakly  acid  potato  as  of  the  strongly 
acid.  According  to  Katschkowski,  a  hyper- 
acidity, even  0-7  to  0-8  per  cent,  of  hydro- 
chloric acid,  produces  a  lasting  spasm  of 
the  pylorus.27  Al chough  in  our  experi- 
ments we  did  not  note  so  pronounced  an 
effect,  we  found  nevertheless  that  the 
hyperacidity  caused  a  retardation  of  the 
passage  of  food  from  the  stomach,  a  result 
explained  by  reasons  already  stated. 
Some  of  the  other  conditions  affecting  gastric  discharge,  which 
Hedblom  and  I  studied,  were  the  consistency  of  the  food,  the 
presence  of  gas  in  the  stomach,  the  temperature  of  the  food,  and 
irritation  of  the  colon.  The  results  can  be  briefly  stated. 

To  obtain  information  regarding  the  effects  of  varying  con- 
sistency and  other  mechanical  factors  on  the  gastric  discharge, 
observations  were  made  on  more  or  less  viscous  samples  of  potato 
and  on  hard  particles  mixed  with  the  food.  Before  diluting  the 
potato,  it  was  baked,  in  order  to  drive  off  most  of  the  water. 


Centimetres 
S  g  8  g  g  « 

\ 

1       / 

/ 

i 

•  ' 

/ 

i 

_J' 

i 

' 

/ 

/ 

i 

•V 

i 

I/ 

• 

1 

Tlours 
FIG.  16. 

The  heavy  line  is  the 
curve  (for  the  second 
half-hour)  when  po- 
tato is  fed  normally  ; 
the  light  line,  when 
fed  with  0-25  per 
cent,  acidity  (HC1)  ; 
and  the  dash  line, 
when  fed  with  1  per 
cent,  acidity. 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS        121 


Two  series  of  observations  were  made.  In  the  first  series  no 
water  was  added  ;  the  potato  when  mixed  with  bismuth  sub- 
nitrate  and  ready  for  feeding  was  very  thick  and  doughy.  In  the 
second  series  water  was  added  until  the  mixture  was  of  the  con- 
sistency of  thin  gruel.  The  volume  fed  in  all  cases  was  25  c.c. 
The  results  with  these  extremes  should  be  compared  with  the 
results  when  potato  of  the  standard  consistency  (intermediate 
between  the  extremes)  is  fed.  As  the  curves  in  Fig.  17  (A)  show 
graphically,  the  rates  of  discharge  of  the  same  kind  of  carbo- 
hydrate food,  thick  or  diluted,  are  nearly  the  same  ;  indeed,  the 
rates  of  discharge  do  not  differ  among  themselves  enough  to 


Z 


2     0 


FIG.  17. 

A.  The  light  continuous  line  is  the  curve  for  potato  of  standard  consistency  ; 

the  heavy  continuous  line,  for  thick,  doughy  consistency  ;  the  dash  line, 
for  thin,  gruelly  consistency  —  5  cases  each. 

B.  The  heavy  line  is  the  curve  for  lean  beef  of  standard  consistency  ;  the  light 

line,  that  for  lean  beef  of  thin,  gruelly  consistency. 

permit  any  noteworthy  significance  to  be  attributed  to  the 
varying  consistencies. 

The  dilution  of  protein  food  might  be  expected  to  have  a 
different  effect  from  the  dilution  of  carbohydrate.  If  protein 
food  is  diluted  with  water,  evidently,  in  a  given  amount,  less 
protein  is  present  to  unite  with  acid  than  would  be  present  if  the 
same  amount  were  given  undiluted.  To  test  this  supposition,  lean 
beef  was  fed  after  being  shredded  and  mixed  with  water  to  a  thin, 
gruelly  consistency.  A  comparison  of  the  curves  in  Fig.  17  (B) 
shows  that  the  dilution  of  the  protein  food,  and  the  reduction 
thereby  of  the  material  uniting  with  the  acid  of  the  gastric  juice, 
tends  toward  a  more  rapid  discharge  of  the  protein  from  the 
stomach. 


122          THE   MECHANICAL   FACTORS    OF   DIGESTION 


40 


30 


20 


10 


The  factor  of  consistency  of  protein  food  is  important  in 
relation  to  the  differing  results  reported  by  different  investigators. 
Thus,  Cohnheim  found,28  by  observations  through  a  duodenal 
fistula,  that  the  emptying  of  the  stomach  began  about  fifteen 
minutes  after  feeding  a  dog  finely  chopped  meat  mixed  with 
water,  and  Lang  reported  that  the  first  slight  discharges  of  gastric 
contents  did  not  occur  until  at  least  fifteen  minutes  after  feeding 
his  dogs  200  grammes  of  fibrin.  Moritz,  on  the  other  hand,  who 
also  used  the  fistula  method  on  dogs,  observed  that  the  exit  of 
the  gastric  contents  began  about  three-quarters  of  an  hour  after 
feeding  200  grammes  of  raw  meat.  My  own  experience  with 
proteins  of  standard  consistency  accords 
with  that  of  Moritz.  The  discrepancy 
between  the  concordant  observations  of 
Cohnheim  and  Lang  and  the  concordant 
observations  of  Moritz  and  myself  is  prob- 
ably due  to  a  difference  in  consistency  of  the 
protein  food.  Certainly,  my  results  were 
well  within  the  limits  set  by  Moritz,  and 
did  not  show  nearly  so  long  a  delay  in  the 
first  discharge  of  meat  from  the  stomach  as 
was  reported  by  Koux  and  Balthazard.29 

Few  observations  as  to  the  relation  be- 
tween hard  food-masses  and  gastric  dis- 
charge have  been  reported.  Moritz30  found 
in  experiments  on  a  dog  with  a  duodenal 
fistula  that  finely  chopped  sausage  began  to 
leave  the  stomach  in  forty-five  minutes, 
whereas  coarse  unchopped  sausage  did  not 
begin  to  leave  for  two  hours.  In  my  first  paper  on  the 
stomach31  I  reported  that  hard  particles  repeatedly  pushed  up 
to  the  pylorus  checked  the  outgo  of  food  from  the  stomach. 
Since  improved  methods  permitted  a  careful  testing  of  this 
statement,  Hedblom  and  I  repeated  the  observations,  giving 
small  irregular  pieces  of  dried  starch  paste  with  the  standard 
potato. 

In  Fig.  18  the  normal  discharge  is  compared  graphically  with 

the  discharge  when  the  same  food,  with  hard  particles  added,  was 

fed.     There  is  a  marked  retardation  of  the  outgo  of  food  from  the 

stomach  when  hard  particles  are  present. 

Food  finely  divided  is  sometimes  fed  in  order  to  spare  the 


Hours 

FIG.  18. 

The  heavy  line  is  the 
normal  curve  for 
potato ;  the  light 
line,  the  curve  when 
hard  particles  are 
present  in  the  food 
— 10  cases. 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS        123 


s20 

O 
10 


stomach.  That  results  not  easy  to  anticipate  may  follow  was 
shown  by  Cohnheim's  observations  on  a  dog  with  a  duodenal 
fistula.  The  stomach  emptied  itself  of  50  grammes  of  finely 
divided  meat  in  an  hour  and  thirty-five  minutes.  When  the 
same  amount  was  given  in  large  lumps,  the  stomach  required 
almost  an  hour  longer  to  empty  itself.  The  coarser  meat, 
however,  was  discharged  almost  entirely  dissolved,  whereas 
nearly  half  of  the  finely  divided  meat  emerged  in  unbroken 
particles.  As  Cohnheim  pointed  out,  the  "  easily  digested," 
finely  divided  meat  did  indeed  spare 
the  stomach,  but  it  placed  more  work  in 
the  small  intestine.32 

The  usual  presence  of  gas  in  the  fundus 
of  the  human  stomach  has  already  been 
mentioned.  When  a  person  reclines, 
this  gas  of  course  changes  location  ;  and 
if  the  person  lies  on  his  back,  the  gas 
takes  a  position  under  the  anterior 
surface  of  the  stomach.  That  the  pres- 
ence of  a  body  of  gas  in  the  stomach 
might  affect  the  exit  of  food  has  appar- 
ently not  been  much  considered.  Yet 
with  the  X  rays  peristaltic  waves  can  be 
seen  moving  over  an  accumulation  of  gas 
without  either  churning  the  contents  or 
propelling  them  onward.  The  gas  acts  as 

a  shield,  keeping  the  walls  of  the  stomach  away  from  the  food. 
We  desired  to  learn  how  a  considerable  amount  of  gas  in  the 
stomach  might  effect  the  discharge. 

The  animals  were  first  fed  the  standard  amount  of  food.  Air 
was  then  introduced  into  the  stomach  while  the  animals  were 
under  observation  ;  thus  the  distension  of  the  stomach  walls 
could  be  easily  regulated.  In  a  few  instances  eructations  nearly 
emptied  the  stomach  during  the  first  hour  ;  more  air  was  then 
introduced  until  approximately  the  original  volume  was  restored. 

The  average  figures  for  fourteen  cases  are  compared  with  the 
average  figures  for  normal  conditions  in  Fig.  19.  As  was  to  be 
expected,  these  average  figures  cover  a  wide  variation  in  the 
effects  produced  by  the  presence  of  gas.  In  few  cases,  however, 
was  there  any  effect  except  a  retardation  of  the  discharge  into 
the  intestine.  This  result  has  been  noted  repeatedly  in  other 


0      k     1  2  3 

Hours 

FIG.  19. 

The  heavy  line  is  the  nor- 
mal curve  for  potato  ; 
the  light  line,  that  for 
potato  when  gas  is  pres- 
ent in  the  stomach. 


124          THE   MECHANICAL  FACTORS    OF  DIGESTION 

instances  in  which  gas  appeared  in  the  stomach  spontaneously* 
Thus,  in  one  case  in  which  fibrin  was  fed,  and  in  which  the  peri- 
staltic waves  could  be  clearly  seen  passing  over  the  gas  in  the 
stomach,  the  discharge  was  as  follows  : 

Hours  after  feeding  ..  ..  . .     *     1       2       3'0       4-0       5 

Centimetres  of  fibrin  when  gas  was  present  ..00       0     lO'O     17'0     22 

Centimetres  of  fibrin,  average  of  four  normal  cases     4     8     21     29*5     32'5     32 

Such  cases  of  spontaneous  accumulation  of  gas  seemed  to  be 
associated  with  atony  and  enfeebled  peristalsis.  When  the  air 
was  experimentally  introduced,  however,  peristalsis,  when  ob- 
served, was  normal  in  rate  and  intensity. 

With  peristalsis  normal,  how  may  the  retardation  of  the  dis- 
charge, noted  in  the  above  experiments,  be  explained  ?  That 
the  distension  of  the  stomach  walls  prevented  them  from  exerting 
a  direct  propelling  action  on  the  food  was  distinctly  visible. 
Only  at  one  surface  was  there  contact  of  the  wall  with  the  food. 
Since  gas  slips  to  and  fro  more  readily  than  fluid  or  semi-fluid 
contents,  it  prevents  the  normal  action  of  the  peristaltic  waves. 
The  retardation  due  to  gas  is  a  result  which  evidently  might  be 
different  in  man  and  in  the  cat.  In  the  upright  position  of  man 
any  gas  in  the  stomach  naturally  rises  to  the  fundus,  and  the  food 
then  lies  in  the  region  of  active  peristalsis.  But  in  the  prone 
position  of  man  gas  in  the  stomach  may  interfere  with  peristaltic 
activities  quite  as  much  as  it  does  in  the  cat. 

Observers  who  have  studied  the  effects  of  heat  and  cold  on  the 
motor  functions  of  the  alimentary  canal  have  reported  various 
results.  Liideritz33  exposed  the  stomach  and  intestines  of 
rabbits  in  a  bath  of  normal  salt  solution  which  was  gradually 
cooled.  He  saw  no  change  until  a  temperature  of  28°  to  30°  C.  was 
reached — below  28°  the  movements  gradually  ceased.  Oser  M 
states  that  low  temperatures  close  the  pylorus,  but  that  higher 
temperatures,  up  to  37°  C.,  have  no  such  effect.  According  to 
Miiller,35  low  temperatures  have  a  quieting,  even  a  paralyzing 
effect  on  the  movements  of  the  stomach,  whereas  high  tempera- 
tures increase  gastric  peristalsis.  These  statements  accord  with 
the  observation  of  Schiile,36  and  Leven  and  Barret,37  that  warm 
water  leaves  the  stomach  much  faster  than  cold ;  but  they  do  not 
seem  to  accord  with  Miiller's  own  results  that  both  hot  and  cold 
fluids  leave  the  stomach  more  slowly  than  fluids  at  body 
temperature. 

In  such  studies  the  time  required  for  the  equalization  of  the 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS        125 

ingested  food  to  the  temperature  of  the  body  is  important,  for 
probably  the  temperature  effects  diminish  as  the  equalization 
takes  place.  By  use  of  maximum  thermometers,  Winternitz38 
observed  that  thirty  minutes  after  drinking  500  c.c.  of  cold  water 
the  temperature  of  the  gastric  contents  was  only  0-6°  C.  lower 
than  general  bodily  temperature.  On  a  patient  with  gastric 
fistula,  Quincke39  obtained  similar  results  when  cold  water  was 
taken,  and  further  found  that  water  at  40°  C.  reached  body 
temperature  within  ten  minutes.  According  to  Quincke,  hot  or 
cold  water  reaches  body  temperature  sooner  than  lukewarm  milk. 
As  Miiller  points  out,  the  stomach  is  in  a  high  degree  able  to  bring 
food  of  widely  differing  temperature  quickly  to  the  temperature 
of  the  body,  a  function  doubtless  dependent  on  the  central 
position  of  the  organ  in  the  body  and  on  the  rich  blood-supply  in 
its  walls  and  in  the  surrounding  structures. 

Since  the  stimulating  influence  due  to  variations  of  temperature 
is  present  for  only  a  comparatively  short  interval,  the  influence 
exerted  might  be  correspondingly  short ;  but  the  possibility  of 
the  effect  outlasting  for  some  time  the  period  of  stimulation  must 
be  considered.  In  the  following  experiments  to  determine  the  rate 
of  discharge  of  hot  and  cold  solid  foods,  the  conditions  of  experi- 
mentation were  quite  normal.  Care  was  taken  to  keep  the  food 
at  the  temperature  stated  until  all  had  been  fed. 

In  two  cases  in  which  the  hot  food  was  given,  the  potato  was 
kept  in  a  dish  surrounded  by  a  large  quantity  of  water  at  50°  to 
55°  C.  during  the  period  of  feeding,  and  the  animals  were  fed  from 
a  spoon.  In  the  other  cases  the  food  was  given  by  means  of  a 
syringe,  and  was  delivered  into  the  stomach  at  a  temperature  of 
approximately  60°  C.  The  cold  food  was  fed  in  a  frozen  condition, 
and  reached  the  stomach  in  frozen  lumps. 

The  only  change  from  the  normal  in  the  rate  of  discharge  of 
food,  hot  or  cold,  was  a  slight  acceleration,  but  this  change  was 
so  slight  as  to  be  inconsiderable.  In  none  of  the  cases  was  there 
observed  any  notable  variation  from  the  usual  peristalsis. 

In  a  series  of  X-ray  observations  made  by  C.  K.  Metcalf,  hot 
and  cold  applications  applied  from  one  to  forty  minutes  to  the 
abdomen  of  healthy  cats  produced  no  appreciable  alteration 
in  gastric  peristalsis.  It  continued  without  interruption  and 
without  measurable  change  of  rate.  These  results  are  quite  in 
harmony  with  the  statement  of  Lommel40  regarding  his  similar 
experiments  on  dogs.  On  the  other  hand,  as  Murphy  and  I  have 


126         THE    MECHANICAL   FACTORS    OF   DIGESTION 

reported,41  excessive  cooling  of  the  stomach  and  intestines,  by 
introducing  cold  sterile  salt  solution  into  the  abdominal  cavity, 
may  be  followed  by  increased  activity  of  intestinal  peristalsis. 
But  this  is  a  procedure  causing  changes  of  temperature  in  the 
bowel  too  great  to  be  produced  by  any  external  applications. 
/"  The  conclusion  seems  justified  that  changes  in  the  temperature 
/  of  the  food  do  not  influence,  in  healthy  animals,  for  any  consider- 
able time,  either  gastric  peristalsis  or  the  rate  of  discharge  from 
I  the  stomach. 

All  the  statements  made  thus  far  regarding  the  action  of  the 
pylorus  have  had  reference  to  conditions  not  attended  by  any 


cm. 


« 

30 
20 
10 

Hou] 

/ 

\ 

/ 

/ 

\ 

/ 

\ 

/ 

\ 

/ 

^ 

^ 

/ 

X 

s 

/ 

^ 

x^ 

/ 

. 

>^ 

^- 

. 

•8   4     1             2             3             4            5             6 

FIG.  20. 

The  continuous  line  represents  the  normal  curve  for  potato  ;  the  dot  line,  the 
typical  condition  immediately  following  intestinal  operation  near  the 
pylorus.  Gastric  peristalsis  was  seen  at  every  observation  after  the  first 
half-hour. 

pathological  change.  When  pathological  states  arise,  however, 
the  normal  action  may  be  profoundly  altered. 

An  illustration  of  such  disturbance  of  the  functions  of  the 
pyloric  sphincter  was  given  in  the  observation  made  by  Murphy 
and  myself  directly  after  high  intestinal  section  and  suture. 
Gastric  peristalsis  was  not  interfered  with,  but  for  almost  six 
hours  after  recovery  from  anaesthesia  the  pylorus  remained 
tightly  closed  against  the  peristaltic  pressure,  and  did  not  permit 
the  food  (potato)  to  pass  into  the  injured  gut42  (see  Fig.  20).  As 
we  pointed  out,  there  is  a  remarkable  coincidence  between  the 
period  of  delay  of  the  discharge  from  the  stomach  and  the  period 
required  for  the  primary  cementing  of  intestinal  wounds. 

Hedblom  and  I  were  interested  to  learn  whether  any  effect  on 
gastric  discharge  could  be  demonstrated  after  causing  irritation 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS        127 

of  the  colon.  The  irritation  was  produced  by  injecting  a  few 
drops  of  croton-oil  into  the  caecum  through  a  small  median  in- 
cision in  the  abdominal  wall.  The  operation,  performed  under 
ether,  did  not  cause  any  subsequent  signs  of  discomfort  in  the 
animals.  The  next  day  they  were  fed  the  standard  potato,  and 
observed.  Comparison  of  the  standard  curve  for  potato  with  the 
curve  representing  the  average  figures  of  four  cases  in  which  the 
colon  was  irritated  (Fig.  21)  shows  at  once  noteworthy  differ- 
ences. Not  only  was  the  gastric  discharge  much  slower  when  the 
colon  was  irritated,  but  the  passage  of  the  food  through  the  small 
intestine  was  greatly  retarded.  The  normal  curve  drops  mainly 
because  of  the  passage  of  material  into  the  large  intestine.  When 
the  colon  was  irritated,  the  curve  failed  to  drop  throughout  eight 


40 


,30 


I20 
I 
10 


\ 


"      >2     1  2  3  4  5  6  78 

Hours 

FIG.  21. 

The  heavy  line  is  the  normal  curve  for  potato  ;  the  light  line,  the  curve  after 
croton-oil  has  been  injected  into  the  colon. 

hours,  whereas  the  normal  curve  begins  to  drop  at  the  end  of  two 
hours.  Normally,  potato  begins  to  appear  in  the  colon  at  the 
end  of  two  or  three  hours ;  under  the  conditions  of  the  present 
experiment,  however,  it  did  not  appear  in  the  colon  until  six  or 
seven  hours  had  elapsed.  In  all  cases  food  was  still  present  in  the 
stomach  at  the  end  of  seven  hours,  though  normally  the  stomach 
is  emptied  of  most  of  this  food  in  about  three  hours. 

Whether  injury  to  the  upper  small  intestine,  and  irritation  of 
the  colon,  affect  gastric  evacuation  through  an  alteration  of 
gastric  secretion  has  not  been  ascertained.  There  are  patho- 
logical conditions  of  the  stomach,  however,  in  which  gastric 
secretion  is  disturbed,  and  in  which  the  acid  control  of  the  pylorus 
certainly  is  in  abeyance.  Cohnheim  has  described  a  dog  which, 


128         THE  MECHANICAL  FACTORS    OF  DIGESTION 

though  recovering  from  gastric  catarrh  and  possessed  of  a  good 
appetite,  still  secreted  no  gastric  juice.  When  meat  was  fed,  it 
passed  through  the  pylorus  in  a  short  time  wholly  undigested. 
Thus  the  small  intestine  was  overwhelmed  with  a  mass  of  unpre- 
pared material,  and  exposed  in  turn  to  the  possibility  of  a 
secondary  disturbance  of  its  own  functions.43 

In  achylia  gastrica,  likewise,  the  absence  of  acid  does  not  lead 
to  a  retention  of  food  in  the  stomach  ;  indeed,  it  is  likely  to  depart 
with  unusual  rapidity.  But  evacuation  in  the  absence  of  an  acid 
reaction  is  only  one  problem  to  be  settled  either  in  achylia 
gastrica  or  in  such  cases  of  gastric  catarrh  as  that  instanced 
by  Cohnheim.  Pancreatic  secretion  without  the  natural  acid 
stimulus  in  the  duodenum  needs  quite  as  much  to  be  investigated 
and  explained. 

As  shown  by  these  examples,  only  after  the  discovery  of  natural 
relations  is  the  character  of  disturbed  relations  revealed.  If  in 
spite  of  disturbed  relations  the  processes  concerned  continue  to  be 
serviceable  to  the  organism  as  a  whole,  an  adaptation  to  the  new 
conditions  must  have  occurred.  The  ability  of  organs  to  adapt 
their  functioning  gradually  to  pathological  states  is  well  known  in 
many  instances.  This  adaptation,  however,  must  be  studied  by 
itself  as  a  special  subject.  Thus,  after  the  normal  physiology  of 
the  pylorus  is  made  clear,  it  becomes  of  interest  to  know  to  what 
extent  and  in  what  manner  disturbances  in  the  stomach  and 
duodenum  are  attended  by  changes  in  the  pyloric  reflex  which  are 
compensatory.  The  fact  that  compensations  may  occur  is  not  an 
argument  against  the  normal  functioning.  The  activities 
occurring  in  the  pathological  absence  of  gastric  juice  do  not  affect 
the  great  array  of  evidence  in  favour  of  the  normal  acid  control  of 
the  pylorus,  just  as  compensated  aortic  regurgitation  does  not 
prove  that  the  semilunar  valves  have  no  function.  We  are 
thoroughly  justified,  therefore,  in  supporting,  by  all  the  favour- 
able evidence  here  reviewed,  the  conclusion  that  acid  above  opens 
and  acid  below  closes  the  pyloric  passage. 


REFERENCES. 

1  Tobler,  Ztschr.  f.  physiol.  Chem.,  1905,  xlv.,  pp.  197,  198  ;  Lang,  Biochem. 
Ztschr.,  1906,  ii.,  p.  240. 

2  Khigine,  Arch,  des  8c.  Bid.,  1895,  ill,  p.  461. 

3  Pawlow,  The  Work  of  the  Digestive  Glands,  London/ 1902,  pp.  97,  103  - 
also  Fermi,  Arch.  f.  Physiol.,  Suppl.,  1901,  p.  76. 

4  Lintwarew,  Biochem.  Gentralbl.,  1903,  i.,  p.  96. 


CORRELATING   FUNCTIONS    OF  THE   PYLORUS        129 

5  Boldireff,  Centralbl.  /.  Physiol.,  1904,  xviii.,  p.  457. 

6  Cohnheim,  Physiol.  d.  Verdauung  u.  Ernlihrung,  Bsrlin,  1908,  p.  168. 

7  Dolinsky,  Arch,  des  Sc.  Biol.,  1895,  iii.,  p.  424. 

8  Volhard,  Ztschr.  f.  klin.  Med.,  1901,  xlii.,  p.  429. 

9  Levites,  Ztschr.  f.  physiol.  Ohem.,  1906,  xlix.,  p.  276. 

10  Levites,  loc.  cit.,  p.  279. 

1  Moore  and  Rockwood,  J.  Physiol.,  1897,  xxi.,  p.  64. 

12  Pawlow,  loc.  cit.,  p.  51. 

13  Openchowski,  Centralbl.  f.  Physiol.,  1899,  iii.,  p.  4  ;  Oser  (Ztschr.  /.  klin 
Med.,  1892,  xx.,  p.  288)  states  that  vagus  stimulation  completely  closes  the 
open  pylorus.     See  also  May,  J.  Physiol.,  1904,  xxxi.,  p.  270. 

4  Moritz,  Ztschr.  f.  Bid.,  1901,  xlii.,  p.  584. 

15  See  Gley  and  Rondeau,  Oompt.  rend.  Soc.  de  Bid.,  Paris,  1893,  xlv.,  p.  517  ; 
Roux  and  Balthazard,  Arch,  de  Physiol.,  1898,  xxx.,  p.  90. 

16  Moritz,  loc.  cit.,  p.  589  ;  also  Carnot  and  Chassevant,  Gompt.  rend.  Soc.  de 
Biol.,  Paris,  1906,  lx.,  p.  866. 

17  Pawlow,  loc.  cit.,  p.  94. 

L8  Cannon,  Am.  J.  Physiol.,  1904,  xii.,  p.  399. 

19  London  and  Sulima,  Ztschr.  f.  physiol.  Ohem.,  1905,  xlvi.,  p.  233. 

20  Pawlow,  loc.  cit.,  p.  96. 

21  London  and  Sulima,  loc.  cit.,  pp.  215,  220. 
12  See  Fermi,  loc.  cit.,  p.  59. 

23  London  and  Sulima,  loc.  cit.,  p.  212. 

24  Moritz,  loc.  cit.,  pp.  589,  590. 

25  See  Chittenden,  Mendel,  and  Jackson,  Am.  J.  Physiol.,  1898,  i.,  p.  207. 

26  Pawlow,  loc.  cit.,  pp.  138,  139. 

17  Katschkowski,  Arch.  /.  d.  ges.  Physiol.,  1901,  Ixxxiv.,  p.  48. 
28  Cohnheim,  Munchen.  med.  Wchnschr.,  1907,  liv.,  p.  2581. 

!9  Roux  and  Balthazard,  Arch,  de  Physiol.,  1898,  xxx.,  p.  91. 
30  Moritz,  Verhandl.  d.  deut.  Naturforscher  und  Aerzte,  1893,  p.  25. 

51  Cannon,  Am.  J.  Physiol.,  1898,  i.,  p  359. 

J2  Cohnheim,  Munchen.  med.  Wchenschr.,  1907,  liv.,  p.  2582. 

33  Liideritz,  Arch.  f.  path.  Anat.,  1889,  cxvi.,  p.  53. 

34  Oser,  Ztschr.  f.  klin.  Med.,  1892,  xx.,  p.  287. 

35  Miiller,  Ztschr.  f.  didt.  und  physikal.  Therap.,  1904,  viii.,  p.  587. 
56  Schiile,  Ztschr.  f.  klin.  Med.,  1896,  xxix.,  p.  81. 

37  Leven  and  Barret,  Eadioscopie  Gastrique  et  Maladies  de  VEstomac,  Paris 
1909,  p.  73. 

38  Winternitz,  "  Physiologic  Bases  of  Hydro  therapy,"  in  A  System  of  Physio- 
logic Therapeutics,  Philadelphia,  1902,  ix.,  p.  41. 

39  Quincke,  Arch.  f.  exper.  Path,  und  Pharmakol.,  1888,  xxv.,  p.  380. 

40  Lommel,  Munchen.  med.  Wchnschr.,  1903,  L,  p.  1634. 

11  Cannon  and  Murphy,  Ann.  Surg.,  1906,  xliii.,  p.  531. 

42  Cannon  and  Murphy,  loc.  cit.,  p.  515. 

43  Cohnheim,  Physiol.  d.  Verdauung  u.  Erndhrung,  Berlin,  1908,  p.  23. 


CHAPTER  XI 

THE  MOVEMENTS  OF  THE  SMALL  INTESTINE 

THE  longest  portion  of  the  alimentary  canal  is  the  small  intes- 
tine. Its  relative  length  varies,  however,  in  different  animals, 
and  this  variation  is  related  interestingly  to  the  character  of  the 
food.  Carnivorous  animals  as  a  rule  have  a  relatively  shorter 
small  intestine  than  do  herbivorous  animals.  Thus  in  the  cat  the 
tube  is  about  three  times  the  length  of  the  body,  in  the  dog  four 
to  six  times,  whereas  in  the  sheep  and  goat  it  may  be  more  than 
twenty-seven  times  the  body-length.1  The  extensive  surface 
provided  by  this  length  of  gut  is  further  augmented  in  many 
animals  by  the  folds  which  project  inward  and  form  the  "  valvulse 
conniventes."  And  the  mucosa  covering  the  interior  of  all  this 
surface  has  its  area  again  enormously  increased  by  being  disposed 
on  the  finger-like  villi,  which  project  inward  in  countless  myriads 
towards  the  lumen.  Between  this  vast  extent  of  mucosa  and 
the  outer  longitudinal  and  inner  circular  muscle  of  the  intestine 
lie  venous  and  lymphatic  plexuses,  and  the  radicles  of  larger 
vessels  belonging  to  these  two  systems. 

Digestive  juices  secreted  in  the  mouth,  the  stomach,  and  in  the 
duodenum,  have  already  accomplished  marked  alterations  in 
the  food  by  the  time  it  is  pushed  on  into  the  ileum.  Yet  in  this 
extensive  region  the  final  changes  occur,  and  while  here  the 
nutritious  portions  of  the  food  are  almost  completely  digested 
and  absorbed.  The  small  intestine,  therefore,  is  the  very  centre 
of  the  essential  activities  on  which  the  body  depends  for 
nourishment. 

The  mechanical  factors  of  digestion,  as  we  have  seen,  have  the 
functions  of  propelling  the  food,  mixing  it  with  the  digestive 
juices,  and  exposing  the  digested  food  to  the  absorbing  mucosa. 
These  functions,  all  of  them  of  first  importance  in  co-operation 
with  digestion  and  absorption,  are  accomplished  in  the  small 

130 


THE   MOVEMENTS    OF  THE   SMALL  INTESTINE        131 

intestine  by  two  main  types  of  activity — by  the  peristaltic  wave, 
and  by  rhythmic  contractions  of  the  intestinal  musculature. 
When  an  animal  is  first  fastened  to  the  holder,  after  the  food 
has  been  distributed  through  the  intestine  as  shown  in  Fig.  6, 
the  noteworthy  condition  in  most  or  all  of  the  loops  is  the  total 
absence  of  movement.  If  the  animal  remains  quiet,  however, 
only  a  few  moments  elapse  before  peculiar  motions  appear  in  one 
or  another  of  the  loops,  or  perhaps  in  several,  and  last  for  some 
time.  These  motions  consist  in  a  sudden  division  of  one  of  the 
long,  narrow  masses  of  food  into  many  little  segments  of  nearly 
equal  size  ;  then  these  segments  are  again  suddenly  divided, 
and  the  neighbouring  halves  unite  to  make  new  segments,  and 
so  on,  in  a  manner  to  be  more  fully  described.  I  have  called 
this  process  the  "  rhythmic  segmentation  "  of  the  intestinal 


FlG.  22. — DlAGKAM  REPRESENTING  THE  PROCESS  OF  RHYTHMIC 
SEGMENTATION. 

Lines  1,  2,  3,  4,  indicate  the  sequence  of  appearances  in  a  single  loop.  The 
dot  lines  represent  the  regions  of  division.  The  arrows  show  the  relation  of 
the  particles  to  the  segments  they  subsequently  form. 

contents.2    Further    observation   reveals    peristalsis   here   and 
there.     These  phenomena  are  now  to  be  considered  in  detail. 

Rhythmic  segmentation  is  by  far  the  most  common  and  the 
most  interesting  mechanical  process  to  be  seen  in  the  small 
intestine.  The  nature  of  the  process  may  best  be  understood 
by  referring  to  the  diagram,  Fig.  22.  A  mass  of  food  is  seen 
lying  quietly  in  one  of  the  intestinal  loops  (line  1,  Fig.  22). 
Suddenly  an  undefined  activity  appears  in  the  mass,  and  a 
moment  later  constrictions  at  regular  intervals  along  its  length 
cut  it  into  little  ovoid  pieces.  The  solid  string*  is  thus  quickly 
transformed,  by  a  simultaneous  sectioning,  into  a  series  of  fairly 
uniform  segments.  A  moment  later  each  of  these  segments  is 
divided  into  two  particles,  and  immediately  after  the  division 

*  In  lieu  of  any  better  short  expression,  "  string  "  of  food  is  used  to  designate 
the  long,  slender  mass  of  the  contents  lying  in  a  loop  of  the  intestine. 


132          THE   MECHANICAL   FACTORS    OF  DIGESTION 

neighbouring  particles  (as  a  and  b,  line  2,  Fig.  22)  rush  together, 
often  with  the  rapidity  of  flying  shuttles,  and  merge  to  form 
new  segments  (as  c,  line  3,  Fig.  22).  The  next  moment  these 
new  segments  are  divided,  and  neighbouring  particles  unite  to 
make  a  third  series,  and  so  on. 

At  the  time  of  the  second  segmentation  (line  3,  Fig.  22)  the 
particles  at  the  ends  of  the  row  are  left  small.  Observation 
shows  that  these  small  pieces  are  not  redivided.  The  end  piece 
at  A  simply  varies  in  size  with  each  division  ;  at  one  moment  it 
is  left  small,  at  the  next  moment  it  is  full  size  from  the  addition 
of  a  part  of  the  nearest  segment,  and  a  moment  later  is  the  small 
bit  left  after  another  division.  The  end  piece  at  B  (probably  the 
rear  of  the  mass)  shoots  away  when  the  end  mass  is  divided,  and 
is  swept  back  at  each  reunion  to  make  the  large  end  mass  again, 
only  to  be  shot  away  and  swept  onward  with  each  recurrence  of 
the  constrictions. 

The  process  of  repeated  segmentation  thus  continues,  with 
the  little  particles  flitting  toward  each  other,  and  the  larger 
segments  shifting  to  and  fro,  commonly  for  more  than  half  an 
hour  without  cessation.  From  the  beginning  to  the  end  of  a 
period  of  segmentation  the  food  is  seen  to  have  changed  its 
position  in  the  abdomen  to  only  a  slight  extent.  Whether  this 
change  is  a  passing  of  the  food  along  the  loop,  or  a  movement  of 
the  loop  itself,  it  is  impossible  to  tell  from  the  shadows  on  the 
screen.  The  change  of  position,  however,  is  much  less  con- 
spicuous than  the  lively  division  and  redi vision  which  the  mass 
suffers  so  many  times  from  the  busy,  shifting  constrictions. 

From  this  typical  form  of  rhythmic  segmentation  there  are 
several  variations.  Sometimes,  and  especially  when  the  mass 
of  food  is  thick,  the  constrictions  do  not  make  complete  divisions, 
and  are  so  far  apart  that  the  intermediate  segments  are  relatively 
large.  Moreover,  the  constrictions  do  not  take  place  in  the 
middle  of  each  segment,  but  near  one  end.  In  another  variety 
of  segmentation  the  food  is  divided,  and  the  first  divisions  then 
subdivided,  before  any  reunion  occurs.  This  form  of  segmenta- 
tion is  fairly  typical  for  the  constrictions  seen  in  a  small  mass 
advancing  through  the  intestine.  Sometimes  the  divisions  occur 
in  the  middle  of  a  long  string  of  food,  and  leave  the  ends  wholly 
unaffected. 

A  remarkable  feature  in  the  segmentation  of  the  food  is  the 
rapidity  with  which  the  changes  take  place.  The  simplest  way 


THE   MOVEMENTS    OF   THE    SMALL   INTESTINE        133 

of  estimating  the  rate  is  to  count,  not  the  number  of  times  the 
partition  of  the  food  recurs  in  the  same  place,  but  the  number 
of  different  sets  of  segments  observed  in  a  given  period.  Thus 
in  Fig.  22  the  appearances  of  lines  2,  3,  4,  etc.,  would  be  counted, 
and  not  merely  lines  2,  4,  etc.  Repeated  observations  have 
shown  that  the  rate  of  division  in  long,  thin  strands  of  food  may 
commonly  be  as  high  as  twenty-eight  or  thirty  times  in  a  minute 
— i.e.,  a  change  from  one  set  of  segments  to  another  set  every 
two  seconds,  and  a  return  of  the  same  phase  every  four  seconds. 
In  some  cases  the  rate  is  as  low  as  eighteen  to  twenty-three  times 
per  minute.  The  larger  masses  seem  to  be  associated  with  a 
slower  segmentation. 

Segmentation  frequently  continues  for  more  than  half  an  hour  ; 
in  one  instance  it  was  seen  persisting,  with  only  three  short  periods 
of  inactivity,  for  two  hours  and  twenty- two  minutes.  At  the 
rate  of  thirty  segmentations  per  minute,  it  is  clear  that  a  slender 
string  of  food  may  commonly  undergo  division  into  small  par- 
ticles more  than  a  thousand  times  while  scarcely  changing  its 
position  in  the  intestine. 

This  process,  thus  far  described  as  I  saw  it  in  the  cat,  I  have  seen 
also  in  the  white  rat  and  in  the  dog.3  In  the  white  rat  the  changes 
occurred  at  the  rate  of  forty-four  to  forty-eight  per  minute  ;  in  the 
dog,  sometimes  at  a  rate  between  eighteen  and  twenty-two,  at 
other  times  between  twelve  and  fourteen,  per  minute.  The  seg- 
menting movements  I  have  never  seen  in  the  rabbit,  but,  instead, 
rhythmic  to-and-fro  shiftings  of  a  mass  along  the  lumen  of  the 
gut,  rapidly  repeated  for  many  minutes.  In  1905  I  reported 
having  heard  rhythmic  sounds  in  the  human  intestine  at  the 
rate  of  seven  or  eight  per  minute,  and  gave  reasons  for  believing 
that  this  rhythm  was  caused  by  segmenting  movements.4  Two 
years  later  Hertz  was  able  to  observe  the  process  of  segmentation 
in  man.  "  The  shadow  of  the  short  length  of  small  intestine, 
at  first  of  uniform  thickness,  became  constricted  in  its  centre  ; 
the  constriction  increased  until  the  single  shadow  was  more  or 
less  completely  divided  into  two.  Then  each  half  underwent  a 
similar  division,  but  the  two  central  segments  of  the  four  pro- 
duced by  the  second  division  joined  together.  The  new  central 
segment  then  divided  again,  the  segmentation  continuing,  in  one 
case,  at  the  rate  of  ten  divisions  in  a  minute  and  a  half."5  This 
rate  is  approximately  seven  divisions  per  minute,  which  is  about 
the  rate  of  the  rhythmic  sounds  which  I  had  heard. 


134 


THE   MECHANICAL   FACTORS    OF  DIGESTION 


The  process  of  segmentation  in  cats  has  been  observed  also  by 
Hertz  6  and  by  Magnus,7  both  of  whom  used  the  X-ray  method  ; 
and  it  has  been  seen  in  dogs  with  opened  abdomen  by  Henderson,8 
who  likened  the  appearance  to  that  which  would  be  presented  by 
a  column  of  large  frog-hearts  beating  in  such  mutual  co-ordination 
that,  while  numbers  1,  3,  5,  and  7,  are  in  systole,  2,  4,  6,  and  8, 
are  in  diastole,  and  vice  versa.  From  all  this  evidence,  it  is  clear 
that  the  process  is  one  whose  existence  is  thoroughly  well 
established. 

The  appearance  of  the  exterior  of  the  small  intestine  while 
this  process  is  occurring  is  shown  in  Fig.  23.  This  photograph 
was  taken  after  the  animal,  well  anaesthetized,  had  had  its  spinal 

cord  pithed  below  the  brachial 
region,  and  its  abdomen  opened 
under  warm  physiological  salt 
solution.  Active  digestion  was  in 
progress.  A  noteworthy  feature  of 
the  rings  of  constriction,  which 
contrast  with  the  peristaltic  wave, 
is  their  narrowness.  As  these 
narrow  constrictions  occur  the  re- 
gion becomes  pale  and  bloodless. 

The  effect  of  the  process  of  rhyth- 
mic segmentation  proves  it  an 
admirable  mechanism.  The  food 
over  and  over  again  is  brought 
into  closest  contact  with  the  in- 
testinal walls  by  the  swift,  knead- 
ing movement  of  the  muscles.  Thereby  not  only  is  the  undi- 
gested food  intimately  mixed  with  the  digestive  juices,  but 
the  digested  food  is  thoroughly  exposed  to  the  organs  of 
absorption.  Mall9  has  shown  that  contraction  of  the  intestinal 
wall  has  the  effect  of  pumping  the  blood  from  the  sub  mucous 
venous  plexus  into  the  radicles  of  the  superior  mesenteric  vein, 
thus  materially  aiding  the  intestinal  circulation.  Moreover, 
lacteals  loaded  with  fat  will  in  a  few  moments  become  empty 
unless  the  intestine  is  slit  lengthwise  so  that  the  muscles  cannot 
exert  compression.10  The  rhythmic  constrictions,  therefore, 
both  propel  the  blood  in  the  portal  circulation  and  act  like  a 
heart  in  promoting  the  flow  of  lymph  in  the  lacteals.  This 
single  movement,  with  its  several  results,  is  another  excellent 


FIG.  23. — A  PHOTOGRAPH  OF 
THE  SMALL  INTESTINE  SEG- 
MENTING ITS  CONTENTS. 


THE   MOVEMENTS    OF  THE   SMALL  INTESTINE        135 

example  of  bodily  economy.  The  repeated  constrictions 
thoroughly  churn  the  food  and  digestive  fluids  together,  plunge 
the  absorbing  mucosa  into  the  very  midst  of  the  food-masses, 
and  also,  by  compression  of  the  veins  and  lacteals  of  the  intes- 
tinal wall,  serve  to  deport  through  blood  and  lymph  channels 
the  digested  and  absorbed  material. 

There  is  little  doubt  that  segmentation  is  due  to  an  activity 
of  the  intestinal  musculature  similar  to  that  which  causes  the 
so-called  "  pendulum  movement."  This  activity  is  characterized 
by  a  gentle  swaying  motion  of  the  coils,  and  is  accompanied  by 
rhythmical  contractions.  Observers  have  described  it  variously 
as  shortenings  and  narrowings  of  the  gut,  rhythmically  repeated 
at  nearly  the  same  intestinal  circumference  ;n  as  alternating 
to-and-fro  movements  of  the  long  axis  without  changes  in  the 
lumen  ;12  as  local  or  extensive  periodic  contractions  and  relaxa- 
tions mainly  of  the  circular  musculature  ;13  and  as  waves  in- 
volving both  muscular  coats  of  the  intestine,  and  travelling 
normally  from  above  downward  at  a  rapid  rate  (2  to  5  centi- 
metres per  second).14  The  pendulum  movements  have  been 
seen  in  the  dog  and  in  the  rabbit  and  cat.16  In  the  cat,  Bayliss 
and  Starling  noticed  that,  when  the  lumen  of  the  gut  was  dis- 
tended by  a  rubber  balloon,  there  appeared  rhythmical  contrac- 
tions, which  nearly  always  were  most  marked  at  about  the 
middle  of  the  balloon — i.e.t  the  region  of  greatest  tension. 

The  segmenting  movements,  of  course,  do  involve  changes  in 
the  lumen,  and  they  do  not  appear  as  waves.  In  these  respects, 
therefore,  they  do  not  fit  certain  descriptions  of  the  pendulum 
movements.  Segmentation  is,  however,  a  local  contraction  and 
relaxation  of  the  intestinal  musculature  ;  and  its  occurrence, 
usually  at  a  point  midway  between  two  rings  of  constriction, 
where  the  compressed  food  stretches  most  forcibly  the  relaxed 
circular  and  longitudinal  muscles,  indicates  that  it  is  a  response 
to  the  increased  local  tension. 

The  best  known  of  the  intestinal  movements  is  the  peri- 
staltic wave.  It  is  observed  in  two  forms  :  as  a  slowly  advancing 
contraction  which  creeps  through  a  short  distance  in  a  coil, 
and  as  a  swift  movement  sweeping  without  pause  for  much 
longer  distances  along  the  canal.  The  first  form  of  the  wave 
merely  transports  nutriment  from  one  region  to  another  near 
by,  thus  utilizing  different  areas  of  the  mucosa  for  secretion 
and  absorption  ;  the  second  form,  which  may  glide  swiftly  from 


136          THE   MECHANICAL  FACTORS    OF  DIGESTION 


one  end  of  the  canal  to  the  other,  has  the  effect  of  clearing  it  of 
its  contents.  The  first  form  may  retain  the  unqualified  term 
peristalsis  ;  the  second  may  be  distinguished  by  the  term  "  rush- 
ing peristalsis,"  or  "  peristaltic  rush,"  as  suggested  by  Meltzer 
and  Auer.16  I 

The  normal  peristaltic  wave  is  slow.  Its  rate  has  been 
variously  stated  as  1  or  2  centimetres  per  minute,  or  even 
slower.17  By  most  observers  the  wave  is  said  to  move  always 
in  one  direction — from  stomach  to  colon. 

The  contraction  that  occurs  in  rhythmic  segmentation  is 
narrow,  involving  hardly  a  centimetre  of  the  circular  coat ;  the 
contraction  that  occurs  in  peristalsis,  on  the  contrary,  extends 

along  the  canal  for  4  or  5  centi- 
metres. The  difference  can  be 
clearly  seen  by  comparing  Figs.  23 
and  24.  A  much  larger  number 
of  circular  fibres  are  evidently 
engaged  when  food  must  be  pushed 
through  the  canal  than  are  active 
in  any  single  segmenting  contrac- 
tion. 

With  the  X  rays  it  is  commonly 
impossible  to  see  how  a  moving 
mass  of  food  is  related  to  the  end 
of  the  intestine,  and  therefore  it 
is  impossible  to  state  absolutely 
whether  peristalsis  or  antiperistal- 
sis  is  active.  The  relations  can  be 
seen  with  the  fluorescent  screen  only  near  the  stomach  and 
near  the  ileo-colic  valve.  The  evidence  that  advancing  peristalsis 
alone  occurs  normally  is,  as  we  shall  see,  so  overwhelming 
that  we  can  safely  assume  that,  when  food  is  moving  in  loops 
not  visibly  related  to  fixed  points,  it  is  moving  onward. 

When  a  mass  of  food  has  been  subjected  for  some  time  to  the 
segmenting  activity  of  the  intestine,  the  separate  segments, 
instead  of  being  again  divided,  may  suddenly  begin  to  move 
slowly  along  the  loop  in  which  they  lie.  That  this  movement 
is  not  a  swinging  of  the  coil  as  a  whole,  but  a  peristaltic  advance 
of  separate  rings  of  its  circular  musculature,  is  made  probable  by 
the  fact  that  the  succeeding  segments  follow  along  the  same 
path  their  predecessors  have  taken.  The  advance  of  the  little 


FIG.  24. — A  PHOTOGRAPH  OF  A 
PERISTALTIC  WAVE  ON  THE 
SMALL  INTESTINE. 

The  wave  was  pushing  material 
into  the  colon. 


THE   MOVEMENTS    OF  THE   SMALL  INTESTINE        137 

pieces  may  continue  for  7  or  8  centimetres,  when  finally  the 
front  piece  stops  or  meets  other  food.  Then  all  succeeding  pieces 
are  swept  one  by  one  into  the  accumulating  mass,  which  at  last 
lies  stretched  along  the  intestine,  a  solid  string  manifesting  no 
sign  of  commotion. 

Another  form  of  slow  peristalsis  is  frequently  observed  when 
the  food  is  pushed  forward,  not  in  small  divisions,  but  as  a 
large  lump.  The  relatively  long  mass  of  food  is  first  crowded 
into  an  ovoid  shape  as  the  forward  movement  begins.  The 
next  moment  it  is  indented  in  the  middle  by  a  circular  constric- 
tion, which  spreads  it  into  two  portions  along  the  loop.  Now 
both  portions  may  be  cut  in  two.  The  whole  mass  is  at  once 
swept  together  again,  and  slightly  beyond  its  first  position, 
whereupon  the  segmenting  process  is  repeated.  Thus,  with 
many  halts  and  interruptions,  the  food  slowly  advances. 

A  slight  variation  of  the  combined  peristalsis  and  segmentation 
just  described  is  seen  when  the  amount  of  food  is  greater  and 
extends  farther  along  the  intestine.  Under  such  circumstances, 
as  the  mass  moves  forward,  there  appears  just  in  front  of  the 
rear  end,  where  the  distension  is  greatest,  a  constriction  which 
separates  a  piece  from  the  main  body,  and  causes  it  to  shoot 
backward  sometimes  through  the  distance  of  a  centimetre.  The 
main  body  meanwhile  is  not  disturbed.  No  sooner  has  the  rear 
section  been  shot  away  than  it  is  swept  forward  again  into  union 
with  the  rest  of  the  food,  and  the  whole  mass  then  advances 
until  another  interfering  constriction  repeats  the  process. 

Peristalsis  may  become  disturbed  after  a  surgical  operation 
requiring  the  intestine  to  be  severed  and  sutured.  Clinical 
experience  has  not  determined  whether  end-to-end  or  lateral 
methods  of  uniting  the  divided  intestine  are  preferable.  In 
favour  of  the  lateral  junction,  the  argument  has  been  urged18 
that  it  permits  conveniently  a  desirable  large  contact  of  serous 
surfaces — a  condition  said  not  to  be  possible  in  the  end-to-end 
union  without  dangerously  narrowing  the  lumen  of  the  canal, 
and  without  liability  of  producing  death  of  the  tissues  from 
pressure  on  mesenteric  vessels.  The  claims  have  been  made, 
also,  that  lateral  anastomosis  can  be  used  without  regard  to  the 
size  of  the  intestinal  parts  to  be  united,  and  that  with  it  the 
opening  between  the  two  intestinal  ends  can  be  made  as  extensive 
as  may  be  wished.  On  the  other  hand,  the  tendency  of  all 
lateral  unions  of  parts  of  the  alimentary  canal  to  become  nar- 


138          THE   MECHANICAL   FACTORS    OF   DIGESTION 

rowed  has  been  repeatedly  recognized.  And  studies  on  animals 
have  shown  that  indigestible  substances,  such  as  straw  and  hair, 
may  accumulate  at  the  point  of  lateral  union  and  block  the 
passage.19  Such  a  condition,  however,  has  never  been  cited  as 
true  of  man  whose  diet  is  carefully  watched  after  operation. 

Theoretically  there  are  possibilities  of  functional  defect  both 
in  the  end-to-end  and  in  the  lateral  union.  In  the  end-to-end 
junction  two  severed  ends  of  the  intestine  are  sewed  together. 
The  transverse  cutting  of  the  gut  destroys  locally  the  mechanism 
governing  peristalsis,  and  under  these  conditions  there  might 
be  stasis  of  the  food  in  the  region  of  union.  In  lateral  anas- 
tomosis circular  muscle  fibres  of  the  canal  are  cut — the  fibres 
which  force  the  food  onward.  Contraction  of  the  circular 
muscle  singly  in  either  one  or  the  other  of  the  overlapping 
intestinal  ends  cannot  then  force  the  food  onward,  but  must 
simply  shift  the  food  over  into  the  inactive  part.  For  propulsion 
of  the  contents  of  this  region  there  must  be  a  co-ordinated, 
advancing  contraction  of  the  circular  fibres  simultaneously  in 
the  two  apposed  loops.  Undigested  material  is  commonly  found 
as  a  remnant  in  the  region  of  lateral  junction.  Is  there  in  this 
region  a  stasis  of  the  normal  food  material  ? 

In  order  to  test  the  possibilities  of  functional  disturbance, 
F.  T.  Murphy  and  I  made  intestinal  sections  and  resections  in 
animals,  and  then  united  the  severed  gut  either  end-to-end  or 
laterally.  For  two  reasons,  the  operation  was  performed  as  near 
as  possible  beyond  the  delicate  fold  of  mesentery  which  holds 
the  end  of  the  duodenum  in  place  :  the  point  is  fixed  so  that 
the  position  of  the  suture  can  be  recognized  fairly  accurately 
in  observations  with  the  X  rays  ;  and  it  is  so  near  the  stomach 
that  the  observer  does  not  have  to  wait  long  after  feeding  the 
animal  before  the  food  reaches  the  region  he  wishes  to  study. 

Observations  were  made  on  different  animals  one,  four,  seven, 
and  ten  days  after  end-to-end  union  of  the  intestine.  In  no  case 
was  the  slightest  evidence  observed  of  stasis  of  the  food  in  the 
region  of  operation.  The  food  was  passed  along  that  part  of  the 
intestine  as  it  was  passed  along  other  parts. 

The  results  were  quite  different  with  lateral  anastomosis. 
Animals  permitted  to  live  ten  days  or  two  weeks  showed  usually 
the  condition  already  mentioned — a  more  or  less  complete 
blocking  of  the  canal  by  accumulated  hair  and  undigested 
detritus  at  the  opening  between  the  apposed  loops.  To  see 


THE   MOVEMENTS    OF  THE   SMALL   INTESTINE        139 

whether  there  was  a  stoppage  of  the  normal  food  at  the  anas- 
tomosis, animals  were  operated  upon  and  carefully  fed  for  four 
days  on  food  with  little  waste.  Then  they  were  given  a  rather 
thin  boiled  starch  (4  grammes  of  starch  to  100  c.c.  of  water), 
with  an  admixture  of  bismuth  subnitrate.  As  long  as  this  food 
was  passing  through  the  intestine,  some  of  it  was  always  present 
at  the  junction.  And  when  almost  all  the  unabsorbed  material 
was  in  the  colon,  there  still  remained  a  large  mass  filling  the 
widened  lumen  where  the  coils  were  laterally  joined.  Observa- 
tion the  next  day  showed  the  mass  still  at  the  anastomosis. 
Autopsies  on  these  animals  proved  that  the  stasis  of  the  food 
was  not  due  to  previous  accumulation  of  indigestible  waste. 
The  region  of  junction  was  filled,  not  with  hard  material,  but 
with  a  pasty  stuff,  in  physical  characteristics  much  like  that 
seen  ordinarily  in  the  small  intestine,  and  certainly  capable  of 
easy  peristaltic  transportation  through  the  gut.  In  these  cases 
the  two  apposed  coils  evidently  did  not  co-operate  to  propel 
the  enclosed  food.  Any  food  forced  through  the  region  of  union 
was  propelled  by  a  push  from  behind,  a  push  exerted  by  peri- 
stalsis of  the  intact  Wall  driving  new  masses  from  time  to  time 
into  the  accumulation  at  the  junction.  And  when  no  food 
remained  to  act  as  an  intermedium  between  the  accumulated 
mass  in  the  widened  lumen  and  the  pressing  peristalsis  of  the 
intact  gut,  there  was  nothing  to  continue  the  propulsion  through 
the  common  chamber,  and  the  mass  was  left  unmoved. 

Inasmuch  as  stasis  was  not  observed  at  any  time  after  end- 
to-end  union  of  the  severed  gut,  whereas  after  lateral  anastomosis 
ordinary  food  was  stagnant  in  the  region  of  junction,  it  is  clear 
that,  other  things  being  equal,  the  end-to-end  union  is  preferable 
to  the  lateral  for  rapid  return  of  the  normal  functioning  of  the 
canal.  In  time  after  lateral  union  the  canal  may  become  changed 
from  a  crooked  to  an  almost  straight  tube.20  As  such  an  altera- 
tion takes  place,  possibly  there  occurs  a  restitution  of  the  func- 
tional efficiency  of  the  joined  parts.  The  absence  of  this 
functional  efficiency,  however,  certainly  for  some  days,  and  prob- 
ably for  weeks,  after  the  operation,  renders  lateral  anastomosis 
not  an  ideal  procedure.  The  dangers  of  the  end-to-end  union, 
on  the  other  hand,  have  been  largely  obviated  by  recent  improve- 
ments in  the  technique  of  intestinal  surgery. 

As  to  the  claim  made  for  lateral  anastomosis,  that  it  permits 
the  opening  between  the  two  intestinal  ends  to  be  as  large  as 


140 


THE   MECHANICAL   FACTORS    OF  DIGESTION 


desired,  we  must  recognize  that  the  more  extensive  the  cutting 
of  the  circular  muscle,  the  greater  is  the  interference  with  peri- 
staltic activity ;  and  also,  that  the  condition  to  be  desired  is 
not  so  much  a  large  opening  as  an  opening  that  functions 
satisfactorily. 

Although  our  experiments  led  us  to  differ  from  the  opinion  of 
Ashton  and  Baldy,21  that  lateral  union  is  always  desirable,  we 
agree  with  them  as  to  the  danger  of  allowing  the  blind  ends  of  the 
intestinal  loops  in  lateral  union  to  extend  beyond  the  anastomotic 
opening.     If  each  extends  beyond  the  opening,  the  end  of  the 
proximal  loop,  in  our  experience,  is  in  danger  of  becoming  packed 
with  hardened  waste,  and  the  end  of  the  distal  loop  is  likely  to 
invaginate   until   the   invaginated   portion 
fills  the  lumen  in  the  region  of  the  anasto- 
mosis, and  produces  obstruction  (see  Fig.  25). 
The  blocking  of  the   lumen  in  our  ex- 
periments, when  the  intestine  was  united 
laterally,  led  us  to  make  observations  on 
the    movements   of   the   canal  in  case  of 
obstruction.    Even   when   the   obstruction 
was  within  25  centimetres  of  the  pylorus, 
it  did  not  retard  the  discharge  of  food  from 
the  stomach.    As  the  food  collected  in  the 
obstructed  gut,  there   was   seen   in   every 
instance  a  remarkable  exhibition  of  intestinal 
activity.     Ordinarily  in  the  small  intestine, 
as  I  have  stated,  segmentation  is  a  much 
more  common  activity  than  peristalsis.     Over  and  over  again, 
however,  in  these  cases  of  obstruction,  the  food  was  pushed 
toward  the  obstruction  by  repeated  waves  of  peristalsis.     Noth- 
nagel  reported22  increased  activity  of  like  character  above  an 
experimental  obstruction  in  the  small  intestine  of  the  rabbit. 
The  moving  constrictions  in  our  cases  were  evidently  powerful, 
for  as  they  advanced,  the  walls  of  the  canal  in  front  were  bulged 
widely  by  the  compressed  contents  ;  and  when  the  peristaltic 
ring  could  no  longer  withstand  the  pressure  it  was  causing, 
the  contents  squirted  back  through  the  advancing  ring  for  some 
distance  along  the  gut.    No  sooner  had  one  wave  passed  over 
the  accumulated  food  to  the  point  of  blocking  than  another 
would  start  and  go  over  the  same  course  again,  or  a  series  of 
rhythmic  contractions  would  occur,  dividing  the  contents  into 


A 


FIG.  25.  —  DIAGRAM 
SHOWING  EFFECT  OF 
Too  GREAT  OVER- 
LAPPING OF  LOOPS 
IN  LATERAL  UNION. 

Proximal  loop  (A)  im- 
pacted, distal  loop 
(B)  invaginated. 


THE   MOVEMENTS    OF   THE    SMALL   INTESTINE        141 

large  segments,  and  sometimes  separating  them  widely  from 
one  another.  The  numbered  parts  in  Fig.  26  are  tracings  of 
the  sequence  of  changes  in  the  shadows  of  the  food  during  a  few 
moments  of  observation  about  an  hour  and  a  half  after  feeding 
boiled  gluten-flour.  Similar  activities,  though  not  so  violent, 
were  seen  an  hour  previous.  Other  cases,  observed  during  a 
longer  period,  showed  this  same  vigorous  squeezing  and  churning 
of  the  accumulated  food,  alternating,  however,  with  periods  of 
rest. 

From  these  observations  it  is  clear  that,  when  the  intestine 
is  obstructed,  an  activity  is  aroused  which  must  tend  to  com- 


FIG.  26. — TRACINGS  OF  THE  SHADOWS  OF  THE  CONTENTS  OF  AN  OBSTRUCTED 
LOOP  OF  INTESTINE,  SHOWING  THE  SEQUENCE  OF  CHANGES  THROUGH 
SEGMENTATION  AND  PERISTALSIS  DURING  A  FEW  MOMENTS  OF  OBSERVATION 
ABOUT  AN  HOUR  AND  A  HALF  AFTER  FEEDING. 

In  the   condition  represented  by  No.  4  there  was  repeated  peristalsis,  with 
regurgitation  of  the  food  through  each  advancing  peristaltic  ring. 

pensate  for  the  obstruction,  and  work  to  obviate  it.  These 
results  support  the  contention  made  in  the  discussion  of  gastro- 
enterostomy,  that  kinks  and  sharp  bends  in  the  intestine  normally 
have  food  forced  through  them  by  peristalsis.  A  kink  was 
artificially  produced  by  turning  a  loop  back  on  itself  for  about 
4  centimetres,  and  sewing  together  the  surfaces  in  contact. 
Observation  five  days  later  proved  that  the  food  was  pushed 
around  the  very  sharp  bend  of  the  tube  by  the  vigour  of  the 
peristaltic  waves. 

The  possibility  of  waves  moving  in  either  direction  along  the 
gut  anyone  can  readily  prove  by  repeating  Engelmann's  observa- 
tion on  the  intestine  of  an  animal  recently  killed.23  To  what 


142  THE   MECHANICAL   FACTORS    OF   DIGESTION 

extent  the  conditions  in  reversed  loops  may  become  similar  to 
those  in  the  dead  animal  is  not  known.  That  antiperistalsis 
does  not  occur  in  the  small  intestine  seems  to  be  proved  by 
Mall's  experiment24  of  reversing  a  portion,  sewing  it  in  place, 
and  then  rinding  that  undigested  material  did  not  pass  the 
reversed  region,  but  collected  at  the  upper  end.  Other  observers,25 
after  reversing  various  lengths  of  the  gut,  have  confirmed  Mall's 
conclusion  that  peristalsis  does  not  reverse  in  the  reversed  por- 
tion, but  they  have  found  further  that  thoroughly  digestible 
food  can  be  pushed  through  reversed  loops,  when  not  too  long, 
without  any  noticeable  difficulty.  The  addition  of  solid  in- 
digestible stuff,  such  as  pieces  of  straw  and  bone,  at  once  caused 
stasis  at  the  upper  junction. 

Opposed  to  the  conclusion  that  there  is  no  antiperistalsis  of 
the  small  intestine  is  the  clinical  evidence  that  in  cases  of  in- 
testinal obstruction  continued  vomiting  of  offensive  decomposed 
material  may  occur  after  the  stomach  has  been  repeatedly 
washed — the  so-called  "  fsecal  vomiting." 

In  relation  to  this  conflict  of  evidence,  our  observations  on 
an  animal  with  about  20  centimetres  of  the  intestine  reversed 
just  beyond  the  duodenal  band  are  of  interest.  The  first 
observation  was  made  six  days  after  the  operation.  At  the 
autopsy  not  long  thereafter,  a  heap  of  indigestible  stuff  was 
found  obstructing  the  canal  at  the  upper  suture.  With  the 
X  rays  the  food  had  been  seen  again  and  again  leaving  the 
stomach.  After  collecting  in  the  duodenum,  it  moved  onward, 
with  occasional  segmentation,  through  a  definite  course  which 
was  traced  on  transparent  paper.  Finally  it  began  to  accu- 
mulate in  the  region  of  the  upper  suture.  About  a  half -hour 
after  ingestion  the  whole  mass  began  to  be  tossed  about  by  the 
alternating  periods  of  segmentation  and  peristalsis  characteristic 
of  the  state  of  obstruction.  Suddenly  the  mass  was  divided  near 
the  enlargement  of  the  upper  suture  ;  then  the  proximal  portion 
was  moved  rapidly  back  along  the  course  which  had  been  traced, 
even  up  to  the  pylorus.  This  reversed  movement  of  the  food 
was  seen  repeatedly  with  perfect  distinctness.  The  method 
used  did  not  permit  seeing  the  contractions  of  the  intestinal 
wall ;  only  the  effects  on  the  food  could  be  observed.  But  if 
food  had  been  moved  forward,  as  in  this  instance  it  was  certainly 
moved  backward,  the  movement  must  assuredly  have  been 
attributed  to  peristalsis. 


THE   MOVEMENTS    OF  THE   SMALL  INTESTINE        143 

Further  evidence  of  the  possibility  of  antiperistalsis  in  the 
small  intestine  has  been  brought  forward  by  several  observers 
who,  some  time  after  the  operation,  have  watched  directly  the 
activities  of  a  reversed  part  of  the  gut.  More  than  three  months 
after  operation,  Kelling  saw  in  the  exposed  intestine  the  contents 
moved  towards  the  colon  through  the  reversed  portion  by 
distinct  peristaltic  waves.26  Enderlen  and  Hess  were  able  to 
produce  downward  peristalsis  in  a  reversed  loop  by  electrical 
stimulation.27  And  after  a  considerable  interval  had  followed  the 
reversal,  Beer  and  Eggers,28  and  McClure  and  Derge,29  reported 
seeing  peristaltic  waves  moving  distinctly  from  the  upper  to  the 
lower  junction.  In  time,  therefore,  conditions  may  arise  which 
alter  the  function  of  the  intestinal  wall. 

The  swift  wave  of  peristalsis  that  may  sweep  over  the  entire 
length  of  the  small  intestine  in  about  a  minute,  or  over  extensive 
reaches  of  the  gut,  was  observed  first  by  v.  Braam-Houck- 
geest  30  in  rabbits  with  exposed  intestines,  killed  by  asphyxia. 
The  confused  turnings  and  squirmings  of  the  coils  as  the  con- 
traction rushes  along  have  caused  the  phenomenon  to  be  desig- 
nated as  "  Rollbewegung  "  and  the  "  vermicular  wave."  As 
already  stated,  Meltzer  and  Auer  have  suggested  the  term  "  peri- 
staltic rush  " — complete  or  incomplete,  according  as  all  or  only 
part  of  the  small  intestine  is  involved. 

This  peculiar  type  of  intestinal  activity  Starling  was  inclined  to 
regard  as  an  exaggeration  of  the  rhythmic  type31;  on  the  other 
hand,  Mall  placed  it  in  a  class  by  itself  and  declared  that  its 
service  was  to  rid  the  intestine  rapidly  of  irritating  substances. 
That  this  rushing  wave  is,  however,  truly  peristaltic  in  character 
was  proved  by  the  observation  of  Meltzer  and  Auer,  that  it 
consists  of  a  contraction  preceded  by  a  completely  relaxed  section 
of  the  gut,  through  which  the  contents  are  rapidly  driven.  They 
were  able  to  evoke  the  phenomenon  at  will  in  rabbits  by  intra- 
venous injections  of  pairs  of  substances  producing  stimulation 
and  inhibition  of  intestinal  activity.  The  most  effective  pair  was 
ergot  (stimulant)  and  calcium  chloride  (depressant).32 

Peristaltic  rush  probably  occurs  in  conditions  of  abnormal 
irritation  of  the  gut,  and  may  be  the  characteristic  activity  when 
a  purge  is  given.  With  the  X  rays  I  have  seen  rapjd  peristalsis 
produced  in  the  small  intestine  by  injecti  . 

Under  normal  conditions,  the  only  simikfr^^cuir^i^^ 
peristalsis  is  that  frequently  observably  w^lrt^f^ti^^K^^^;,  ^A 


144          THE   MECHANICAL   FACTORS    OF  DIGESTION 

segmented  in  the  duodenum,  is  carried  swiftly  onward  through  a 
number  of  coils  before  being  released. 

Having  considered  the  motor  activities  exhibited  by  the  small 
intestine,  we  may  now  turn  our  attention  to  the  mechanical  treat- 
ment which  the  food  receives  in  traversing  it.  As  we  have 
learned,  the  chyme  is  not  forced  from  the  stomach  by  every  wave 
that  passes  over  the  vestibule,  but  only  at  intervals.  When  the 
pylorus  relaxes,  the  food,  under  considerable  pressure,  is  squirted 
along  the  duodenum  for  2  centimetres  or  more.  Careful  watch- 
ing of  this  food  shows  that  usually  it  lies  for  some  time  in  the 
curve  of  the  duodenum,  until,  with  additions  from  the  stomach, 
a  long,  thin  string  is  formed.  While  resting  in  this  place  it  is 
exposed  to  the  outpouring  of  bile  and  pancreatic  juice.  All  at 
once  the  string  becomes  segmented,  and  the  process  continues 
several  minutes,  thoroughly  mixing  the  digestive  juices  with  the 
chyme.  In  this  region  the  alternate  positions  of  the  segments 
are  sometimes  far  apart,  and  the  to-and-fro  movement  of  the 
particles  may  be  a  relatively  extensive  and  very  energetic 
swinging.  Finally,  the  little  segments  are  united  into  a  single 
mass,  or  formed  in  groups,  and  begin  to  move  forward.  Peri- 
stalsis here,  as  already  mentioned,  is  much  more  rapid  than 
normal  peristalsis  elsewhere  in  the  small  intestine.  The  masses, 
once  started,  go  flying  along,  turning  curves,  whisking  hither  and 
thither  in  the  loops,  moving  swiftly  and  continuously  forward.* 
After  passing  on  in  this  rapid  manner  for  some  distance,  the  food 
is  collected  in  thicker  and  longer  strings,  resembling  the  strings 
seen  characteristically  in  the  other  loops.  Towards  the  end  of 
digestion,  the  small  masses  shot  out  from  the  stomach,  after  a  few 
segmentations,  may  move  on  in  the  rapid  course  without  being 
accumulated  in  a  larger  mass  until  the  swift  movement  ceases. 

During  the  first  stages  of  digestion  in  the  cat's  small  intestine 
the  food  usually  lies  chiefly  on  the  right  side  of  the  abdomen  ; 
during  the  last  stages  the  loops  on  the  left  side  usually  contain  the 
greater  amount  of  food.  In  these  loops  the  food  remains  some- 
times for  an  hour  or  more  with  no  sign  of  movement.  All  at  once 
a  mass  may  begin  to  undergo  division  and  reunion,  division  and 
reunion,  over  and  over  again,  in  the  manner  described  above  as 
rhythmic  segmentation.  After  a  varying  length  of  time  the 
activity  wanes,  and  the  little  segments  are  carried  forward 

*  If  this  process  is  true  also  of  man,  the  region  beyond  the  duodenum  would 
naturally  be  "  jejune." 


THE    MOVEMENTS    OF  THE   SMALL  INTESTINE        145 

individually  and  later  brought  together,  or  united  and  moved  on 
as  a  single  body,  or  left  quietly  for  some  time  without  further 
change.  Thus  by  a  combined  process  of  kneading  and  peristaltic 
advance  the  food  is  brought  to  the  ileo-colic  valve  to  enter  the 
large  intestine. 

In  studying  the  passage  of  food  through  the  small  intestine  of 
a  woman  with  a  fistula  at  the  ileo-colic  junction,  MacFadyen, 
Nencki,  and  Sieber,33  noted  a  considerable  variation  in  the  time 
between  the  ingestion  of  the  food  and  its  appearance  at  the  fistula. 
Peas,  for  example,  arrived  at  the  colon  on  one  occasion  two  and  a 
quarter  hours,  and  on  another  occasion  five  and  a  quarter  hours, 
after  being  eaten.  Demarquay,34  who  studied  a  case  similar,  but 
apparently  less  normal,  reported  also  a  wide  variation  in  the  time 
of  the  first  appearance  of  food  at  the  fistula. 

The  X-ray  method  as  I  used  it  did  not  permit  a  statement  of 
the  moment  when  the  food  first  entered  the  colon  ;  only  the  first 
regular  observation  after  food  had  entered  could  be  reported. 
Since  the  observations  were  an  hour  apart,  the  results,  except  in 
their  negative  aspect,  were  not  as  exact  as  could  be  desired.  The 
following  figures,  therefore,  represent  for  each  foodstuff  the 
number  of  cases  in  which,  at  the  hours  stated,  a  shadow  was  first 
seen  in  the  colon  : 

Hours  after  feeding              ..  ..2  3         4  5  6         7  8* 

Carbohydrates  (sixteen  cases)                  1  6         4  4  —        1  — 

Proteins  (sixteen  cases)       ..  ..—  12  2  72  2 

Fats  (sixteen  cases)              ..  ..      —  23  7  2        2  — 

This  table  indicates  a  variation  similar  to  that  observed  in  man. 
Although  the  mean  time  after  eating  at  which  material  reaches 
the  colon  is  about  four  hours  for  carbohydrates,  about  six  hours 
for  proteins,  and  about  five  hours  for  fats,  the  divergence  from 
the  mean  in  each  of  the  three  cases  is  considerable.  Among  the 
carbohydrates  used,  the  divergence  was  chiefly  due  to  moistened 
crackers,  which  in  four  instances  arrived  at  the  colon  only  after 
five  or  seven  hours.  And  among  proteins,  also,  the  divergence 
was  chiefly  due  to  one  food — boiled  haddock — which  reached  the 
colon  about  two  hours  earlier  than  most  of  the  other  proteins. 
As  a  general  statement,  we  may  say  that  in  the  cat  carbohydrates 
reach  the  large  intestine  about  one  hour  before  fats,  and  about 
two  hours  before  proteins.  After  time  is  allowed  for  the  later 

*  In  two  cases  no  material  had  reached  the  colon  at  the  end  of  seven  hours  ; 
they  are  regarded  as  belonging  to  an  eight-hour  class. 

10 


146          THE   MECHANICAL  FACTORS    OF  DIGESTION 

start  of  proteins  from  the  stomach,  the  probability  still  remains 
that  proteins  pass  through  the  small  intestine  much  more  slowly 
than  do  carbohydrates,  whereas  fats  have  a  rate  intermediate 
between  the  two. 

The  relatively  rapid  movement  of  carbohydrates  through  the 
canal  may  be  associated  with  the  presence  of  insoluble  cellulose. 
Hedblom  and  I  found  that  coarse,  branny  food  stimulates  gastric 
peristalsis ;  it  also  passes  through  the  small  intestine  with  unusual 
speed.  In  X-ray  observations  on  man,  Hertz  noted  that  after  an 
ordinary  meal  a  shadow  appeared  in  the  caecum  after  intervals 
varying  between  three  and  a  half  and  five  hours,  with  an  average 
interval  of  four  hours  and  twenty-two  minutes.35  When  a  horse 
eats  oats,  the  waste  may  go  through  the  much  longer  intestine  of 
that  animal  in  less  time.36  The  greater  length  of  the  small 
intestine  in  herbivorous  animals  compared  with  carnivorous, 
mentioned  at  the  beginning  of  this  chapter,  is  possibly  associated 
with  the  greater  rapidity  of  movement  of  plant  food  and  the 
necessity  of  digesting  out  the  valuable  contents  from  cellulose 
surroundings.37 

In  experimental  animals  I  have  never  seen  any  marked  delay 
in  the  passage  of  food  through  the  small  intestine  except  under 
experimentally  disturbing  conditions,  such,  for  example,  as 
irritation  of  the  colon  (see  p.  127).  Hertz  has  reported  that,  in  his 
observations  on  human  beings,  delay  in  the  small  intestine  has 
occurred  only  in  cases  of  lead-poisoning.  If  the  evacuation  of  the 
bowels  is  retarded,  therefore,  and  no  obstruction  of  the  lumen 
exists,  the  chances  are  almost  wholly  in  favour  of  the  large 
intestine  as  the  place  of  retention. 


REFERENCES. 

1  Fermi  and  Repetto,  Arch.  f.  Physiol.,  1901,  Suppl.,  p.  85. 

2  Cannon,  Am.  J.  Physiol.,  1902,  vi.,  p.  256. 

3  Cannon,  Am.  J.  Physiol.,  1903,  viii.,  p.  xxi. 

4  Cannon,  Am.  J.  Physiol.,  1905,  xiv.,  p.  346. 

5  Hertz,  Guy's  Hosp.  Rep.,  1907,  Ixi,  p.  409. 

6  Hertz,  loc.  cit.,  p.  409. 

7  Magnus,  Arch.  /.  d.  ges.  Physiol.,  1908,  cxxii.,  p.  216. 

8  Henderson,  Am.  J.  Physiol.,  1909,  xxiv.,  p.  71. 

9  Mall,  Johns  Hopkins  Hosp.  Rep.,  1896,  i.,  p.  68. 
L0  Mall,  loc.  cit.,  p.  47. 

«  Ludwig,  Lehrb.  d.  Physiol.  d.  Mensch.,  Leipzig  and  Heidelberg,  1861, 
11.,  p.  615. 

12  Raiser,  Beitr.  z.  Kennt.  d.  Darmbeweg.  (Dissertation),  Giessen,  1895,  p.  7 ; 
and  Nothnagel,  Die  Erkrank.  d.  Darms  und  d.  Peritoneum,  Wien,  1898,  i., 
Darmbewegung,  p.  1. 


THE   MOVEMENTS    OF  THE   SMALL   INTESTINE        147 

13  MalUoc.  cit.,  p.  48. 

14  Bayliss  and  Starling,  J.  Physiol.,  1899,  xxiv.,  p.  103. 

5  Bayliss  and  Starling,  J.  Physiol.,  1901,  xxvi.,  pp.  127,  134. 

16  Meltzer  and  Auer,  Am.  J.  Physiol.,  1907,  xx.,  p.  266. 

17  See  Cash,  Proc.  Roy.  Soc.,  1886,  xli.,  p.  227. 

8  Kiittner,  Beitr.  z.  klin.  Chir.,  Tubingen,  1896,  xvii.,  p.  505. 

19  Senn,  Ann.  Surg.,  1888,  vii.,  p.  265 ;  and  Reichel,  Miinchen.  med.  Wchnschr., 
1890,  xxxvii.,  p.  197. 

20  Edmunds  and  Ballance,  Med.-chir.  Trans.,  London,  1896,  p.  263. 

21  Ashton  and  Baldy,  Med.  News,  1891,  Iviii.,  p.  235. 

12  Nothnagel,  Beitr.  z.  Physiol.  u.  Pathol.  d.  Darmes,  Berlin,  1884,  p.  28. 

23  Engelmann,  Arch.  f.  d.  ges.  Physiol.,  1871,  iv.,  p.  35. 

24  Mall,  loc.  cit.,  p.  93. 

25  See  Sabbatani  and  Fasola,  Arch.  Itcd.  de  BioL,   1900,  xxxiv.,  p.   195  ; 
Prutz  and  Ellinger,  Arch.  /.  klin.  Chir.,  1902,  Ixvii.,  p.  964  ;  1904,  Ixxii.,  p.  415. 

26  Kelling,  Arch.  /.  klin.  Chir.,  1900,  Ixii.,  p.  326. 

27  Enderlen  and  Hess,  Deutsche  Ztschr.  f.  Chir.,  1901,  lix.,  p.  240. 

28  Beer  and  Eggers,  Ann.  Surg.,  1907,  xlvi.,  p.  582. 

29  McClure  and  Derge,  Johns  Hopkins  Hosp.  Bui.,  1907,  xviii.,  p.  473. 

30  v.  Braam-Houckgeest,  Arch.  f.  d.  qes.  Physiol.,  1872,  vi.,  p.  267. 

31  Starling,  Schcifer's  Text-Book  of  Physiology,  Edinburgh  and  London,  1900, 
ii. ,  p.  329. 

32  Meltzer  and  Auer,  loc.  cit.,  p.  281. 

13  MacFadyen,  Nencki,  and  Sieber,  J.  Anat.  and  Physiol.,  1891,  xxv.,  p.  393. 

34  Demarquay,  L' Union  Med.,  1874,  xviii.,  p.  906. 

35  Hertz,  loc.  cit.,  p.  410. 

36  See  Goldschmidt,  Ztschr.  f.  physiol.  Chem.,  1887,  xi.,  p.  299. 

37  See  Cohnheim,  Physiol.  d.  Verdauung  u.  Erndhrung,  Berlin,  1908,  p.  33. 


CHAPTER  XII 

THE  MOVEMENTS  OF  THE  LARGE  INTESTINE 

IN  carnivorous  mammals  digestion  occurs  principally  in  the 
stomach  and  small  intestine  ;  the  caecum  is  either  rudimentary  or 
absent.  In  herbivores,  as  a  rule,  either  the  stomach  is  amplified 
and  subdivided,  as  in  ruminants,  or,  if  the  stomach  is  simple, 
there  is  usually  compensation  in  a  large  sacculated  colon  and 
caecum.  The  caecum  is  the  seat  of  extensive  bacterial  fermenta- 
tion ;  food  rich  in  cellulose  may  remain  in  this  region  for  days, 
undergoing  changes  which  result  in  its  being  utilized  by  the  body.1 
Even  when  the  caecum  is  of  moderate  size  or  rudimentary,  as  in 
the  cat,  prolonged  retention  of  the  material  delivered  by  the  small 
intestine  is  provided  for  in  the  reversed  peristalsis  which  prevails 
in  the  proximal  colon.  Food  remnants  may  have  begun  to  enter 
the  large  intestine  two  or  three  hours  after  the  food  was  ingested, 
and  they  may  have  left  the  small  intestine  entirely  empty  at  the 
end  of  seven  hours,  and  yet  be  found  in  part  in  the  proximal  colon 
at  the  end  of  twenty-four  hours.  While  stagnating  in  this 
region,  rich  in  bacterial  flora,  the  contents  are  subjected  to 
fermentative  decomposition,  and  the  last  bit  of  nutriment  here 
disappears. 

The  energetic  chemical  processes  occurring  in  the  small  intes- 
tine demand  a  fluid  medium.  By  the  salivary  and  gastric  glands 
large  amounts  of  fluid  are  poured  out  upon  the  food.  This  is 
augmented  by  the  secretions  of  the  pancreas  and  liver  and  the 
wall  of  the  gut  itself.  Throughout  the  small  intestine,  although 
water  is  readily  absorbed,  the  digestive  products  are  maintained 
in  a  semi-fluid  state.  Ease  of  movement  through  the  canal  and 
ready  exposure  of  the  food  for  absorption  are  doubtless  thereby 
favoured.  When  the  large  intestine  is  reached,  however,  and 
practically  all  of  the  serviceable  substances  have  entered  the 
body,  the  water  is  no  longer  necessary.  In  the  proximal  colon, 
therefore,  water  is  also  removed. 

148 


THE   MOVEMENTS    OF  THE   LARGE   INTESTINE        149 

As  the  waste  is  crowded  onward  into  the  distal  colon,  it  takes 
on  more  and  more  the  peculiar  faecal  consistency.  According  to 
Roith,2  the  contents  of  the  transverse  colon  in  man  are  generally 
as  firm  as  those  of  the  rectum.  As  these  fsecal  accumulations  are 
periodically  pushed  into  the  rectum  they  are  discharged  from  the 
body.  The  motor  activities  subserving  these  various  functions 
performed  by  the  large  intestine  we  shall  now  consider. 

When,  in  the  cat,  the  large  intestine  is  full,  palpation  through 
the  abdominal  wall  will  demonstrate  that  the  material  in  the 
distal  colon  usually  consists  of  hard  incompressible  lumps,  while 
that  in  the  proximal  colon  is  so  soft  that  the  walls  of  the  gut  can 
be  easily  pushed  together.  The  condition  of  the  contents  in 
these  two  regions  seems  to  indicate  a  rough  division  of  the  large 
intestine  into  two  parts,  and  the  mechanical  activities  of  these 
two  parts  verify  the  differentiation.  In  the  descending  colon 
the  material  is  gripped  by  persistent  rings  of  tonic  constric- 
tion (see  Fig.  27).  In  the  ascending  and  transverse  colon  and 
in  the  caecum,  by  far  the  most  common  movement  is  anti- 
peristalsis. 

The  first  food  to  enter  the  colon  from  the  small  intestine  in  the 
cat  is  pressed  by  antiperistaltic  waves  towards  the  cisecum,  and  all 
new  food  as  it  enters  is  also  affected  by  them.  The  waves  follow 
one  after  another  in  a  series  like  the  peristaltic  undulations  of  the 
stomach  (see  Figs.  28  and  32),  beginning  at  the  nearest  tonic 
constriction  (Figs.  27  and  32).  They  rarely  run  continuously  for 
a  long  time.  When  the  colon  is  full  it  is  usually  quiet.  The  first 
sign  of  activity  is  an  irregular  undulation  of  the  walls,  then  very 
faint  constrictions  passing  along  the  gut  toward  the  caecum.  As 
they  continue  coursing  over  the  intestine,  they  become  deeper  and 
deeper  until  there  is  a  marked  bulging  between  successive  con- 
strictions. After  these  deepest  waves  have  been  running  for  a 
few  minutes,  the  indentations  grow  gradually  less  marked,  until  at 
last  they  are  so  faint  as  to  be  hardly  discernible.  The  final  waves 
are  sometimes  to  be  observed  only  in  the  neighbourhood  of  the 
tonic  constriction. 

Such  a  period  of  antiperistalsis  lasts  from  two  to  eight  minutes, 
with  an  average  duration  of  four  or  five  minutes.  The  periods 
recur  at  varying  lengths  of  time.  In  one  instance  a  period  began 
at  1.38  p.m.  and  was  repeated  at  2.6,  2.34,  2.55,  3.15,  and  at  3.36, 
when  the  observation  ceased.  In  another  instance  a  period 
began  at  2.43  p.m.,  and  was  repeated  at  2.57  and  at  intervals  of 


150          THE  MECHANICAL  FACTOKS    OF  DIGESTION 

from  ten  to  fifteen  minutes  thereafter  while  the  animal  was  being 

watched. 

The  waves  have  nearly  the  same  rate  of  recurrence  as  those  in 
the  stomach  ;  about  five  and  a  half  waves  pass  a  given  point  in  a 
minute.  This  rate  has  proved  fairly  constant  in  different  cats  and 


FIG.  27. — RADIOGRAPH  SHOWING  THE  REGION  OF  Toxic  CONSTRICTIONS 
(DESCENDING  COLON)  AND  THE  REGION  or  ANTEPERISTALSIS  (TRANSVERSE 
AND  ASCENDING  COLON). 

at  different  stages  in  the  process  of  digestion.     In  one  case, 
however,  the  waves  passed  at  the  rate  of  nine  in  two  minutes. 

The  stimulating  effect  of  rectal  injections  on  the  movements  of 
the  small  intestine  has  already  been  mentioned.  Enemata  have 
also  pronounced  stimulating  action  on  the  antiperistalsis  of  the 
colon.  Usually,  the  almost  immediate  result  of  a  rectal  injection 


THE    MOVEMENTS    OF  THE   LARGE   INTESTINE         151 

of  warm  water  is  the  appearance  of  deep  antiperistaltic  waves, 
which  often  continue  running  for  a  long  period.  In  one  case, 
after  an  injection  of  50  c.c.  of  warm  water,  the  waves  followed 
one  after  another  with  monotonous  regularity  during  an  observa- 
tion lasting  an  hour  and  twenty  minutes. 

Two  other  movements  have  been  observed  in  the  ascending 
colon,  but  they  are  rare  appearances.  The  first  of  these  was  a 
serial  sectioning  of  the  contents,  noticed  in  an  animal  given  castor- 
oil  with  the  food.  A  constriction  separated  a  small  segment  in 
the  caecum ;  another  constriction  then  cut  ofi  a  segment  just 
above  the  first,  and  with  the  disappearance  of  the  first  con- 
striction the  two  separated  segments  united.  A  third  segmenta- 
tion took  place  above  the  second,  and  the  changes  occurred 
again.  Thus  the  whole  mass  was  sectioned  from  one  end  to  the 
other,  and  no  sooner  was  that  finished  than  the  process  began 
again  and  was  repeated  several  times.  A  slight  modification  of 
this  movement  was  observed  in  a  colon  containing  very  little 
food.  The  mass  was  pressed  and  partially  segmented  in  the 
manner  characteristic  of  the  small  intestine,  and  was  thus  again 
and  again  spread  along  the  ascending  colon,  and  each  time  swept 
back  into  a  rounded  form  by  antiperistalsis.  The  second  of  the 
two  movements  mentioned  above  consisted  in  a  gentle  kneading 
of  the  contents.  This  was  caused  by  broad  constrictions  appear- 
ing, relaxing,  appearing,  relaxing,  over  and  over  again  in  the 
same  place.  When  several  of  these  regions  were  active  at  the 
same  time,  they  gave  the  food  in  the  colon  the  appearance  of 
a  restless  undulatory  mass.  Once  a  constriction  occurred  and 
remained  permanently  in  one  place,  while  the  bulging  parts  on 
either  side  of  it  pulsated  alternately,  at  the  rate  of  about  eighteen 
times  in  a  minute,  with  the  regularity  of  the  heart-beat.  Although 
these  phenomena  are  remarkable,  they  are  not  usual,  and  are 
in  no  way  so  important  as  the  antiperistalsis. 

The  passage  of  material  through  the  ileo-colic  valve  seems  to 
stimulate  the  colon  to  activity.  As  a  mass  is  nearing  the  valve 
the  large  intestine  is  usually  quiet  and  relaxed  (Fig.  28,  4.00), 
though  occasionally  indefinite  movements  are  to  be  observed ;  and 
sometimes  just  before  the  mass  reaches  the  end  of  the  ileum  the 
circular  fibres  of  the  colon  in  the  region  of  the  valve  contract 
strongly,  so  that  a  deep  indentation  is  present  there.  The 
indentation  may  persist  several  minutes  ;  it  disappears  as  the 
muscles  relax  just  previous  to  the  entrance  of  new  material.  The 


152          THE   MECHANICAL   FACTORS    OF   DIGESTION 

mass  is  now  moved  slowly  along  the  ileum,  and  is  pushed  through 
the  valve  into  the  colon.  The  moment  it  has  entered,  a  strong 
contraction  takes  place  all  along  the  csecum  and  the  beginning 
of  the  ascending  colon,  pressing  some  of  the  food  onward  ;  and  a 
moment  later  deep  antiperistaltic  waves  (Fig.  28,  4.03)  sweep 
down  from  the  transverse  colon,  and  continue  running  until  the 
caecum  is  again  normally  full  —  i.e.,  for  two  or  more  minutes. 

These  constrictions,  passing  backward  over  the  colon,  do  not 
force  the  normal  contents  back  through  the  valve  into  the  small 
intestine  again.  I  have  seen  hundreds  of  such  constrictions,  and 
only  twice  have  there  been  exceptions  to  this  rule  —  once  under 
normal  conditions,  when  a  small  mass  slipped  back  into  the  ileum  ; 

and   at   another   time  when   a 
large    amount    of    water    had 
been  introduced  into  the  colon. 
The   X-ray   observations   on 
antiperistalsis     of     the     cat's 
proximal   colon  which   I    pub- 
lished in   19023  were  confirmed 
FIG.   28.—  TRACINGS    SHOWING      .      iqfu  hv  Elliott  and  Barrlav- 
CHANGES  WHEN  FOOD  ENTERS  THE 
COLON,  AND  ALSO  THE  FIRST  TONIC     Smith,  who  studied  the  activities 

CONSTRJCTION. 


of   ^  j 

4.00,  the  colon  relaxed  as  food  ap- 

proaches in  the  ileum;   4.03,  the  men   opened  under  warm  salt 

colon  contracted  and  traversed  by  solution.4     They    called     atten- 
antipenstaltic  waves  after  the  food  J 

has  entered.  tion  also  to  a  fact  which  had 

been   overlooked,   that    Jacobi 

had  reported,  in  1890,  colonic  aniiperistalsis  in  the  cat, 
noticed  incidentally  during  a  research  on  colchicum-poisoning.6 
By  the  X-ray  studies  and  by  the  investigations  of  Elliott  and 
Barclay-Smith,  however,  the  reversed  peristaltic  movement  of 
the  proximal  colon  was  definitely  established  as  a  normal  activity. 
These  returning  waves  have  now  been  seen  in  the  dog,6  in  the 
rat  and  guinea-pig,  and  to  some  extent  in  the  rabbit,  hedgehog, 
and  ferret.7  When  a  well-developed  caecum  exists,  there  may  be 
an  interplay  between  its  peristalsis  and  the  antiperistalsis  of  the 
proximal  colon,  as  in  the  rat  ;  or,  as  in  the  rabbit,  the  ca3cum 
may  feed  material  into  the  mixing  apparatus  of  the  proximal 
colon.  In  the  herbivores  which  they  studied,  Elliott  and  Barclay- 
Smith  found  that  sacculation  of  the  proximal  colon  was  associated 
with  churning  movements,  each  sacculus  becoming  at  times  the 
seat  of  swaying  oscillations.  The  greater  the  churning  activity 


THE  MOVEMENTS    OF  THE   LAEGE   INTESTINE        153 

of  the  proximal  colon,  the  more  marked  was  the  sacculation  of  its 
wall. 

The  colon  of  man  is  of  the  sacculated  herbivorous,  rather  than 
of  the  carnivorous  type.  As  all  observations  have  indicated,  the 
sign  of  a  proximal  colon  which  mixes  and  churns  its  contained 
material  is  a  uniform  soft  consistency  of  its  contents.  Only  in 
the  caecum  and  ascending  colon  is  this  condition  realized  in  man  ; 
the  contents  of  the  transverse  colon,  I  have  already  stated,  are 
generally  as  firm  as  those  of  the  rectum.  From  the  nature  of  the 
contents,  Elliott  and  Barclay-Smith  assumed  that  in  man  the 
material  entering  the  proximal  colon  "  is  still  delayed  by  a  back- 
ward current,  still  commingled  by  the  activity  of  the  walls  of 
the  sacculi." 

The  support  for  the  view  that  antiperistalsis  occurs  in  the 
human  proximal  colon  is  at  present  inferential.     In  cases  of 
caecal  fistula,  rectal  enemata  will  often  traverse  the  entire  length 
of  the  colon,  and  escape  through  the  artificial  opening.    In  these 
cases  also,  surgeons  have  endeavoured  to  stop  the  faecal  discharge 
by  transplanting  the  ileum  into  the  transverse  colon,  and  they 
have  found  that  the  discharge  still  continues.    Indeed,  one  case  is 
reported  in  which  the  ileum  was  sewed  into  the  lower  end  of  the 
descending  colon  ;  and  since  the  discharge  through  the  fistula  in 
the  caecum  persisted,  the  colon  was  finally  cut  across,  and  closed 
immediately  above  the  junction  in  order  to  stop  the  backward 
transportation  of  material.8    The  larger  amount  of  contents  in 
the  proximal  colon  has  also  been  considered  evidence  of  anti- 
peristalsis.     Thus,  Koith  has  found  that  the  caecum  and  ascending 
colon  contain  on  an  average  about  twice  the  amount  of  material 
present  in  an  equal  length  of  transverse  colon,  and  three  to  five 
times  as  much  as  an  equal  length  of  descending  colon.9    This 
observation,  however,  might  be  explained  by  the  capacity  of  the 
caecum  being  greater  than  any  other  part  of  the  large  intestine,10 
and  by  its  possessing  a  very  thin  wall.11     Significant  X-ray 
evidence  has  been  brought  forward  by  Stierlin,  who  has  published 
radiographs  showing  that  the  proximal  colon  holds  part  of  the 
food  containing  the  bismuth  salt  after  the  rest  has  passed  on  into 
the  distal  colon,12  and  that  it  retains  this  material  longer  than 
any  other  part  of  the  alimentary  canal.     These  observations,  I 
may  state,  are  in  harmony  with  the  conditions  in  experimental 
animals  in  which  antiperistalsis  has  been  demonstrated.   Stierlin 
has  also  pointed  out  that  the  caecum  is  the  widest  part  of  the 


154          THE   MECHANICAL   FACTOKS    OF   DIGESTION 

entire  intestinal  canal,  and  that  in  this  region  the  separation  of 
the  contents  in  sacculi  or  haustra  is  often  absent  or  only  slightly 
developed.13 

Although  the  escape  through  caecal  fistulas  of  material  intro- 
duced distally  in  the  colon  clearly  demonstrates  a  backward 
current  in  the  human  large  intestine,  and  although  the  great 
volume  of  caecal  contents  and  their  long  retention  are  indicative 
of  antiperistalsis,  the  phenomenon  has  not  yet  been  seen  in  man. 
Hertz  has  testified  to  having  watched  with  the  X  rays  the  shadow 
of  the  human  colon  for  various  periods  in  a  large  number  of 
individuals,  without  seeing  antiperistalsis.  Even  when  an  enema 
containing  bismuth  was  introduced  under  pressure  until  the 
whole  colon  was  visible,  he  saw  no  sign  of  antiperistaltic  activity.14 
Much  weight  should  not  be  given,  however,  to  this  negative 
evidence,  for  in  all  animals  in  which  antiperistalsis  of  the  colon 
has  been  seen,  its  occurrence  has  been  occasional.  In  observa- 
tions on  these  animals,  I  have  had  experiences  that  almost 
parallel  those  of  Hertz  on  man.  Even  in  experimental  conditions 
most  annoying  failure  to  evoke  antiperistalsis  was  common  in 
my  experience  until  the  great  significance  of  the  tonus  ring  as  a 
source  of  the  waves  was  realized — a  relation  to  be  considered 
later.  Possibly  when  tonic  contractions  can  be  produced  in  the 
human  colon  antiperistaltic  waves  will  be  revealed. 

Since  the  circular  coat  of  the  ileum  is  thickened  at  the  junction 
with  the  colon,  Keith15  suggested,  in  1903,  that  in  most  animals, 
probably  including  man,  not  merely  a  mechanical  valve,  but  a 
true  sphincter,  separates  the  large  ard  small  intestines.  The 
next  year  Elliott  proved  physiologically  the  existence  of  such  a 
sphincter  in  the  dog,  by  showing  that  it  was  subject  to  special 
nervous  control  different  from  that  of  neighbouring  parts  of  the 
intestinal  tract.16 

Antiperistalsis  in  the  colon  gives  new  meaning  and  value  to  the 
location  of  a  sphincter  or  valve  at  the  opening  of  the  ileum.  For, 
inasmuch  as  the  valve  is  normally  competent,  the  constrictions 
repeatedly  coursing  toward  it  force  the  food  before  them  into  a 
blind  sac.  The  effect  on  the  contents  must  be  the  same  as  the 
effect  seen  in  the  stomach  when  the  pylorus  remains  closed  before 
the  advancing  waves.  The  confined  material  is  pressed  upon  by 
the  approach  of  each  constriction  ;  but  since  it  cannot  go  onward 
in  the  blind  sac,  and  is,  moreover,  subjected  to  increasing 
pressure  as  the  constriction  comes  nearer,  it  is  forced  into  the 


THE    MOVEMENTS    OF  THE   LARGE   INTESTINE        155 

only  way  of  escape — i.e.,  away  from  the  caecum  through  the 
advancing  constricted  ring.  About  twenty-five  waves  in  the  cat 
affect  thus  every  particle  of  food  in  the  colon  during  each  normal 
period  of  antiperistalsis.  The  result  must  be  again  a  thorough 
mixing  of  the  contents,  and  a  bringing  of  these  contents  into  close 
contact  with  the  absorbing  wall — a  process  which  has  already 
been  variously  repeated  many  times  in  the  stomach  and  in  the 
small  intestine.  The  last  remnants  of  value  in  the  food, 
with  some  of  the  water,  are  here  removed ;  and  the  waste  is 
passed  onward  into  the  distal  colon  to  be  ejected  from  the 
body. 

In  1894,  Griitzner17  published  an  observation  and  made  an 
assumption  about  which  there  has  since  been  much  controversy. 
He  stated  that  when  normal  salt  solution,  holding  in  suspension 
hair,  powdered  charcoal,  or  starch  grains,  is  injected  into  the 
rectum,  it  is  carried  upward  into  the  small  intestine,  and  may 
even  enter  the  stomach.  These  experiments  have  been  repeated 
by  several  observers.  Some  have  confirmed  Griitzner's  results  ; 
others  have  failed,  after  using  most  careful  methods,  to  find  any 
evidence  of  the  passage  of  the  injected  material  back  to  the 
stomach,  and  they  have  declared  that  the  apparent  success  was 
due  to  carelessly  allowing  the  food  of  the  animal  to  become  con- 
taminated with  the  test  materials,  so  that  these  were  introduced 
into  the  stomach  by  way  of  the  mouth. 

By  means  of  the  X  rays  it  is  possible  to  see  just  what  takes 
place  when  a  fluid  is  injected  into  the  rectum.  For  the  purpose 
of  determining  how  nutrient  enemata  are  received  and  acted 
upon  in  the  intestines,  I  introduced  in  large  and  small  amounts 
thin  fluid  masses  and  thick  mushy  masses,  in  different  animals. 
The  enemata  consisted  of  100  c.c.  of  milk,  one  egg,  10  to  15 
grammes  of  bismuth  subnitrate,  and  2  grammes  of  starch,  to  hold 
the  bismuth  powder  in  suspension.  To  make  the  thick  enema,  all 
these  were  stirred  together  and  boiled  to  a  soft  mush  ;  to  make 
the  thin  enema,  all  the  parts  were  boiled  together  except  the  egg, 
which  was  added  after  the  boiled  portion  was  cooled.  The  small 
amount  injected  was  25  c.c. ;  the  large  amount  almost  90  c.c., 
about  the  capacity  of  the  large  intestine  when  removed  from  the 
body.  The  animals  were  given  first  a  cleansing  injection,  and 
after  this  was  effective  the  nutrient  material  was  introduced. 
In  order  to  make  sure  of  the  observation,  a  control  radiograph 
was  first  taken  to  show  no  bismuth  food  present,  and  other 


156          THE   MECHANICAL  FACTORS    OF  DIGESTION 

radiographs  were  taken  at  varying  intervals  after  the  injection 
to  record  the  course  the  food  was  following. 

When  small  amounts  of  nutrient  fluid  were  introduced,  they 
lay  first  in  the  distal  colon.  In  every  instance  antiperistaltic 
waves  were  set  going  by  the  injection,  and  the  material  was 
thereby  carried  to  the  caecum.  When  large  amounts  were 
injected,  they  stopped  for  a  moment  in  the  region  between  the 
second  and  last  third  of  the  colon,  as  if  a  constriction  existed 
there.  Then  a  considerable  amount  of  the  fluid  passed  the  point, 
and  the  antiperistaltic  waves  began  their  action.  In  any  case 
the  repeated  passing  of  the  waves  seemed  to  have  the  effect  of 
promoting  absorption,  for  in  the  region  where  they  continued 
running  the  shadows  became  gradually  more  dim,  and  finally 
the  bismuth  appeared  to  be  only  on  the  intestinal  walls  ;  in  other 
regions — e.g.,  in  the  distal  colon — the  shadows  retained  their 
original  intensity.  Small  injections  were  never,  in  my  experience, 
forced  even  partially  into  the  small  intestine  ;  but  with  the  larger 
amounts,  whether  fluid  or  mushy,  the  radiographs  showed  many 
coils  of  the  small  gut  filled  with  the  bismuth  food. 

The  pressure  required  to  force  the  injected  material  beyond 
the  ileo-colic  sphincter  is  probably  due  largely  to  antiperistalsis 
in  the  colon — a  factor  unknown  to  both  Griitzner  and  his 
opponents.  The  sphincter  which  is  thoroughly  competent  for 
food  coming  normally  from  the  small  intestine  into  the  large  is, 
for  some  unknown  reason,  incompetent  for  a  substance,  even  of 
the  consistency  of  thick  cream,  introduced  in  large  amount  by 
rectum.  When  the  valve  first  permits  the  food  to  enter  the 
ileum,  the  fluid  pours  through,  and  appears  suddenly  as  a 
winding  mass  occupying  several  loops  of  the  intestine.  The 
winding  mass  is  continuous  from  the  valve  to  the  other  end ; 
antiperistalsis  is  therefore  not  visible  in  the  small  intestine  under 
the  circumstances  of  this  experiment.  The  antiperistaltic  waves 
of  the  colon,  however,  continue  running ;  the  proximal  colon  is 
thus  almost  emptied,  and  the  small  intestine  more  and  more 
filled  with  food.  After  a  short  time  the  typical  segmenting 
movements  can  be  seen  in  the  loops,  busily  separating  the  food 
into  small  masses  and  over  and  over  again  dividing  and  redividing 
them. 

I  have  never  seen  injected  material  passed  back  from  the  colon 
as  far  as  the  stomach  ;  but  once,  about  ten  minutes  after  an 
injection  of  100  c.c.  of  warm  water,  the  cat  retched  and  vomited 


THE  MOVEMENTS    OF  THE   LARGE    INTESTINE        157 

a  clear  fluid,  resembling  mixed  water  and  mucus.  In  the  fluid 
were  two  worms,  still  alive,  commonly  found  in  the  intestine. 

As  material  accumulates  in  the  proximal  colon,  we  have  learned 
that  it  is  at  first  confined  there  by  antiperistaltic  waves.  With 
further  accessions,  however,  the  contents  naturally  must  be 
pressed  more  and  more  into  the  distal  colon.  In  the  early  stages 
of  this  accumulation,  while  the  food  lies  chiefly  in  the  proximal 
part,  the  only  activity  of  the  muscular  walls  is  the  antiperistalsis. 
As  the  contents  extend  along  the  intestine,  a  deep  constriction 
appears  near  the  advancing  end,  and  nearly  separates  a  globular 
mass  from  the  main  body  of  the  accumulation.  The  contents 
of  the  large  intestine  progress  farther  and  farther  from  the 
caecum ;  meanwhile  new  tonic  constrictions  appear,  which 
separate  the  contents  into  a  series  of  globular  masses,  which  are 
present  chiefly  in  the  distal  colon  (Fig.  27).  Similar  appearances 
are  observable  in  the  terminal  portion  of  the  rabbit's  colon,  in 
which  deep  circular  constrictions  separate  the  scybalous  masses, 
and  push  them  onward  by  regular  peristalsis.  Comparing  tra- 
cings made  at  rather  long  intervals  (forty-five  minutes),  I  found 
that  as  the  colonic  contents  increased  the  rings  disappeared  from 
the  transverse  colon,  and  were  then  present  with  the  waste 
material  in  the  descending  colon.  Thus  in  the  cat  also  these 
rings,  which  seem  with  short  observation  to  be  remaining  in  one 
position,  are  probably  moving  slowly  away  from  the  caecum, 
pushing  the  hardening  contents  before  them.  The  contents  at 
this  stage  are  no  longer  fluid,  and  consequently  they  must  offer 
considerable  resistance  to  a  force  pushing  them  towards  the 
rectum.  It  is  an  advantage  to  have  this  pultaceous  material  pro- 
pelled in  divisions  rather  than  in  a  uniformly  cylindrical  mass, 
since  the  fibres  along  the  length  of  the  mass  are  thereby  rendered 
effective.  Such  seem  to  be  the  functions  of  the  persistent  rings  : 
to  form  the  waste  matter  into  globular  masses  at  the  end  of  the 
proximal  colon,  and  to  push  these  masses  slowly  onward. 

The  rate  of  progress  of  material  through  the  large  intestine  in 
man  has  been  studied  by  Hertz  with  the  X  rays.  He  states  that 
the  time  required  for  each  part  of  the  colon — ascending,  trans- 
verse, and  descending — is  about  two  hours.  That  is,  about  the 
same  period  is  occupied  in  passing  through  the  2  feet  of  colon 
between  the  caecum  and  the  splenic  flexure  as  through  the 
22|  feet  of  small  intestine.18  The  movements  of  the  human 
colon,  however,  appear  to  be  less  active  at  night  than  during  the 


158          THE   MECHANICAL   FACTORS    OF  DIGESTION 

day.  In  one  individual,  for  example,  a  bismuth  content  was 
present  at  the  end  of  the  descending  colon  eight  hours  after  being 
ingested  at  breakfast ;  but  when  taken  at  10.30  p.m.  it  had  reached 
only  the  end  of  the  ascending  colon  after  twelve  hours.  The 
taking  of  meals  also  is  stimulating  to  the  colon  ;  by  making 
tracings  hourly  after  a  bismuth  breakfast,  Hertz  found  that, 
apart  from  meals,  progress  through  the  colon  was  slow,  but  that 
after  each  meal  there  was  perceptible  advancement  of  the 
contents.  More  progress  occurred,  for  example,  during  the 
dinner-hour  than  during  the  previous  four  hours.19 

According  to  Holzknecht,20  who  in  two  cases  was  fortunate  in 
seeing  the  activities  of  the  human  colon  by  means  of  a  fluorescent 
screen,  the  contents  of  one  section  are  moved  onward  into  an 
empty  distal  section  by  a  sudden  push,  lasting  only  a  few  seconds. 
The  haustral  segmentation  disappeared  just  before  the  advance 
began,  but  reappeared  at  once  when  the  material  became  settled 
in  the  new  position.  Holzknecht  has  suggested  that  by  three  or  four 
such  pushes,  lasting  about  three  seconds,  the  whole  colon  would 
be  traversed.  The  functions  of  the  haustra,  under  these  circum- 
stances, would  probably  be  concerned  with  increasing  surfaces 
for  absorption,  and  not  with  propulsion  of  their  contents. 

The  process  of  clearing  the  colon  is  in  the  cat  a  process  of 
gradual  reduction  of  the  material  present.  The  first  radiograph 
in  Fig.  29  shows  the  appearance  of  material  in  the  colon  at 
3.11  p.m.  Later,  with  a  slow,  sweeping  movement,  the  gut 
swung  around  to  the  position  shown  in  Fig.  29,  3.25.  At  the 
same  time  the  tonic  constrictions  disappeared,  much  as  the 
haustral  indentations  disappear  in  man,  and  were  replaced  by  a 
strong,  broad  contraction  of  the  circular  muscle,  tapering,  the 
contents  off  on  either  side  in  two  cones.  The  region  of  strongest 
contraction  was  apparently  drawn  downward  with  the  rest  of 
the  gut  by  a  shortening  of  the  descending  colon.  As  the  intestine 
swung  around,  more  material  was  forced  into  the  rectum ;  and 
when  the  swinging  of  the  intestine  stopped,  the  constriction 
which  divided  the  lumen  passed  slowly  downward,  and  with  the 
aid  of  the  muscles  surrounding  the  abdominal  cavity  pushed  the 
separated  mass  out  of  the  canal.  After  the  terminal  mass  had 
thus  been  pushed  out,  the  colon,  with  the  remainder  of  its  con- 
tents, returned  to  nearly  its  former  position  (Fig.  29,  3.46). 
About  two  hours  afterward  this  remnant  had  been  spread 
throughout  the  length  of  the  large  intestine  by  means  of  the 


THE   MOVEMENTS    OF  THE   LARGE   INTESTINE        159 


160          THE   MECHANICAL   FACTORS    OF   DIGESTION 

slowly  moving  rings.  Fig.  27  is  a  radiograph  of  the  same  colon 
pictured  in  Fig.  29  ;  the  radiograph  was  taken  at  11.50  a.m.,  and 
at  12.15  p.m.  the  material  in  the  distal  colon  was  forced  out  in 
the  manner  above  described.  Within  three  hours  the  remaining 
portion  had  been  spread  into  the  evacuated  region,  as  shown  in 
Fig.  29,  3.11. 

The  manner  in  which  the  material  is  spread  from  the  region  of 
the  antiperistaltic  waves  into  the  region  of  the  tonic  constrictions 
presents  a  problem.  During  normal  living  new  food  constantly 
arriving  in  the  colon  must  force  the  old  contents  forward,  just  as 
the  later  parts  of  a  meal  force  forward  the  earlier  parts  ;  there 
is  no  doubt,  however,  that  most  of  the  contents  of  the  proximal 
colon  may  be  passed  onward  even  during  starvation.  The 
emptying  of  this  region,  according  to  my  observations,  is  never 
complete ;  for  after  considerable  time  has  elapsed,  and  the  large 
intestine  is  cleared  and  dilated  with  gas,  some  substance  is  still 
to  be  detected  in  the  caecum  and  clinging  to  the  walls  of  the 
ascending  colon,  an  observation  which  Hertz  has  recorded  also 
for  human  beings.21  The  only  activities  manifested  here  are  the 
antiperistaltic  waves,  and  the  strong  tonic  contraction  of  the 
whole  circular  musculature  shown  in  Fig.  28.  It  is  clear  that  the 
latter  activity  would  serve  to  press  into  the  transverse  colon  a 
considerable  portion  of  the  contents  of  the  ascending  colon,  and 
the  remnant  seen  clinging  to  the  walls  would  be  the  part  not  thus 
pressed  forward. 

Twice  I  have  seen  appearances  which  might  account  for  the 
emptying  of  the  first  portion  of  the  large  intestine  in  a  more 
thorough  manner  than  that  above  described.  At  one  time,  with- 
out apparent  stimulation,  a  strong  tonic  contraction  occurred 
along  the  proximal  colon,  which  almost  wholly  forced  out  the 
contents.  This  action  seemed  merely  an  exaggerated  form  of 
the  contraction  observable  after  food  passes  the  ileo-colic  valve. 
At  another  time,  after  a  mass  of  food  had  passed  through  the 
ileo-colic  valve,  after  the  proximal  colon  had  contracted  generally, 
and  the  antiperistaltic  waves  had  coursed  over  it  in  the  usual 
manner,  a  deep  constriction  appeared  at  the  valve  and  ran 
upward  without  relaxation  nearly  the  length  of  the  ascending 
colon,  pushing  the  contents  before  it.  For  an  instant  the  wave 
paused ;  then  the  constriction  relaxed,  and  the  food  returned 
toward  the  caecum.  These  observations  indicate  that  either  a 
general  contraction  of  the  wall  of  the  large  intestine  or  a  true 


THE  MOVEMENTS    OF  THE   LARGE   INTESTINE         161 

peristalsis  may  be  effective  in  pressing  waste  matter  from  the 
region  where  antiperistalsis  is  the  usual  activity  into  the  region 
where  it  may  be  carried  on  to  evacuation. 

The  function  of  the  colon  during  defaecation  has  also  been 
observed  in  the  cat  by  Elliott  and  Barclay-Smith,22  who  found 
complete  agreement  with  the  account  given  above.  In  man  the 
changes  have  been  studied  and  described  by  Hertz,  who  used  the 
X-ray  method.23  As  in  the  cat,  a  relatively  long  column  of 
faeces  is  passed  out  at  one  time ;  Hertz's  tracings  show  that  the 
entire  large  intestine  below  the  splenic  flexure  is  normally 
evacuated  at  a  single  act.  Thereafter,  usually  during  the  next 
twenty-four  hours,  waste  material  accumulates  in  the  distal 
colon.  It  first  stops  at  the  junction  between  the  pelvic  colon 
and  the  rectum,  where  an  acute  angle  offers  some  obstruction  to 
progress.  Then  from  below  upwards  the  pelvic  colon  fills,  and, 
if  more  material  arrives,  it  gathers  progressively  in  the  iliac  and 
descending  colon.  On  becoming  distended  the  pelvic  colon  rises, 
and  widens  its  acute  angle  with  the  rectum,  thus  removing  the 
obstruction  to  advancement  of  faecal  matter.  Some  of  this 
matter  now  entering  the  rectum  leads  to  the  desire  to  defsecate. 
The  common  performance  of  the  act  regularly  after  breakfast  is 
probably  due,  in  part  at  least,  to  stimulation  of  peristalsis  in  the 
colon  by  taking  food,  aided  by  the  muscular  activities  that 
attend  arising  and  dressing.  When  these  procedures  do  not 
result  in  the  natural  "  desire  to  defaecate,"  voluntary  contraction 
of  the  muscles  surrounding  the  abdominal  cavity  may  cause 
some  faeces  to  enter  the  rectum,  and  thus  evoke  the  call. 

When  the  call  to  defaecation  has  come,  the  further  performance 
of  the  act  is  accomplished  primarily  by  increased  intra-abdominal 
pressure — a  result  of  voluntary  contraction  of  the  abdominal 
muscles  and  the  diaphragm.  As  the  diaphragm  contracts,  the 
entire  transverse  colon  is  pushed  downward,  and  the  ascending 
colon  and  caecum  are  forced  into  an  almost  globular  form.  The 
intra-abdominal  pressure,  as  measured  in  the  rectum  during  this 
stage,  may  be  from  four  to  eight  times  the  normal — i.e.,  may  be 
between  100  and  200  millimetres  of  mercury.24  The  pressure 
causes  more  faeces  to  enter  and  distend  the  rectum  and  the  anal 
canal.  The  distension  of  these  parts  now  arouses  reflexes  which 
start  strong  peristaltic  contractions  of  the  colon,  continues  the 
tendency  to  strain  with  the  voluntary  muscles,  and  produces 
relaxation  of  both  anal  sphincters.  Although,  as  here  described, 

11 


162          THE   MECHANICAL  FACTORS    OF  DIGESTION 

the  process  involves  voluntary  factors,  it  is  quite  capable  of  being 
performed  perfectly  by  the  spinal  animal.25 

The  material  below  the  splenic  flexure  is  in  most  cases  thus 
normally  voided,  and  at  the  same  time,  according  to  Hertz's 
tracings,  much  of  the  content  of  the  ascending  colon  and  caecum 
is  pushed  onward  into  the  transverse  colon.  The  sort  of 
peristaltic  activity  of  the  colon  that  Holzknect  has  observed 
occurs,  therefore,  at  the  time  of  defaecation,  and  results  in  an 
advancement  of  the  faecal  contents  in  at  least  two  large  divisions. 
If  approximately  nine  hours  are  required  for  material  to  reach 
the  descending  colon  in  man,  the  waste  from  food  taken  at  eight 
o'clock  in  the  morning  might  be  discharged  at  five  o'clock  in  the 
afternoon.  If  defaecation  should  occur  regularly  at  four  o'clock, 
however,  the  waste  from  breakfast  must  be  retained  for  another 
twenty-four  hours.  Thus,  as  Hertz  has  pointed  out,  the  interval 
between  a  meal  and  the  excretion  of  its  residue  will  vary,  when 
the  bowels  are  opened  regularly  once  a  day,  between  nine  and 
thirty-two  hours,  the  period  depending  on  the  time  of  eating  and 
the  time  of  defaecation. 

The  importance  of  responding  as  soon  as  the  desire  to  defaecate 
arises  is  shown  by  the  observation  that  the  rectum  accommodates 
itself  to  the  presence  of  a  faecal  accumulation,26  and  then 
does  not  produce  the  desire.  If  the  signal  is  not  soon  obeyed 
it  ceases  to  be  given ;  the  faeces  may  then  remain  long  in  the 
rectum  without  calling  forth  sensations,  and  the  defaecation 
reflex  be  to  that  extent  impaired.  As  material  emerges,  there- 
fore, from  the  control  of  automatisms  that  have  governed  its 
passage  through  the  digestive  canal,  and  enters  the  region  where 
voluntary  interference  is  again  possible,  disturbances  are  likely 
to  arise  because  the  automatic  call  for  exit  can  be  voluntarily 
suppressed. 

REFERENCES. 

1  Zuntz  and  Ustjanzew,  Arch.  f.  Physid.,  1905,  p.  403. 
Roith,  Merckel  and  Bonnet's  Arbeiten,  1903,  xx.,  p.  32. 

3  Cannon,  Am.  J.  Physid.,  1902,  vi.,  p.  265. 

4  Elliott  and  Barclay-Smith,  J.  Physid.,  1904,  xxxi.,  p.  272. 
Jacobi,  Arch.  /.  exper.  Pathd.  u.  Pharmakd.,  1890,  xxvii.,  p.  147. 

0  Cannon,  Am.  J.  Physid.,  1903,  viii.,  p.  xxi ;  Henderson,  ibid.,  1909,  xxiv., 
p.  /i. 

7  Elliott  and  Barclay-Smith,  loc.  cit. 

8  Maucaire,  Cong,  de  Chir.,  Paris,  1903,  p.  86. 

10  ?0itti  Mirh'  a',d'  6renz9d.  d.  M.  u.  Chir.,  1908,  xix.,  p.  40. 
Luschka,  Lage  d.  Bauchorg.  d.  Mensch.,  Carlsruhe,  1873,  p.  21. 


THE   MOVEMENTS    OF  THE   LARGE   INTESTINE         163 

11  Toldt,  Sitzungsb.  d.  kais.  AJcad.  d.  Wissensch.,  Vienna,  1894,  ciii.,  Abth. 
iii.,  p.  52.  See  also  Riesinger,  Munchen.  med.  Wchnschr.,  1903,  i.,  p.  1722. 

12JSee  also  tracings  by  Hertz  (Guy's  Hosp.  Rep.,  1907,  Ixi.,  p.  424,  Fig.  10  d  ; 
p.  427,  Fig.  12),  and  by  Holzknect  (Munchen.  med.  Wchnschr.,  1909,  Ivi., 
p.  2402,  Fig.  2  c). 

L3  Stierlin,  Ztschr.  f.  Klin.  Med.,  1910,  Ixx.,  p.  392. 
4  Hertz,  Constipation  and  Allied  Intestinal  Disorders,  London,  1909,  pp.  7,  8. 

15  Keith,  J.  Anal.  Physiol.,  1903,  xxxviii.,  p.  vii. 

16  Elliott,  J.  Physiol.,  1904,  xxxi.,  p.  157. 

17  Griitzner,  Deutsche  med.  Wchnschr.,  1894,  xx.,  p.  897. 

18  Hertz,  loc.  cit.,  p.  9. 

19  Hertz,  loc.  cit.,  p.  18. 

20  Holzknect,  loc.  cit.,  p.  2402. 

21  Hertz,  loc.  cit.,  p.  418. 

22  Elliott  and  Barclay-Smith,  loc.  cit.,  p.  283. 

23  Hertz,  loc.  cit.,  p.  30. 

24  Keith,  Allbutt  and  Kolleston's  Syst.  of  Med.,  1907,  Hi.,  p.  860. 
Sherrington,  Schafer's  Text-Book  of  Physiology,  Edinburgh  and  London, 

ii.,  p.  851. 
Hertz,  loc.  cit.,  p.  426. 


CHAPTER  XIII 

AUSCULTATION  OF  GASTRO-INTESTINAL  SOUNDS 

IN  reporting,  in  1902,  observations  on  the  movements  of  the 
intestines,  I  made  note1  of  an  instance  of  rhythmic  sounds 
accompanying  the  rhythmic  movements  in  the  small  gut.  It 
occurred  to  me  at  that  time  that  the  sounds  heard  over  the 
abdomen  might  indicate  the  mechanical  activities  going  on  in  the 
alimentary  canal  in  man,  but  it  was  not  until  a  few  years  later 
that  my  attention  was  strongly  aroused  to  the  interest  and 
possible  practical  value  of  abdominal  auscultation.2  The  loud 
gurgling  sounds  produced  by  the  intestines  were,  of  course, 
observed  and  recorded  centuries  ago  ;  the  descriptive  designation 
"  borborygmus  "  was  employed  even  by  Hippocrates.  And 
Robert  Hooke,  in  a  remarkable  passage  written  more  than  a 
hundred  years  before  Laennec,  suggested  "that  it  may  be  possible 
to  discover  the  Motions  of  the  Internal  Parts  of  Bodies  ...  by 
the  sound  they  make,  that  one  may  discover  the  works  performed 
in  the  several  Offices  and  Shops  of  a  Man's  Body,  and  thereby 
discover  what  Instrument  or  Engine  is  out  of  order,  what  Works 
are  going  on  at  several  Times  and  lie  still  at  others  "  ;  and  in 
support  of  this  idea  Hooke  mentioned,  among  other  instances, 
the  hearing  of  the  "  Motion  of  Wind  to  and  fro  in  the  Guts."3 
The  suggestion  that  abdominal  sounds  may  be  useful  in  dis- 
covering the  works  of  the  stomach  and  intestines  has,  however, 
received  but  scant  attention.  In  1849,  Hooker  published  an 
essay,4  in  which  he  described  variations  in  the  frequency  and 
intensity  of  intestinal  gurglings  in  the  course  of  different  diseases 
of  the  digestive  organs.  Since  that  time  other  writers  have 
classified  the  sounds  normally  audible  into  splashings,  rattling  or 
rustling  noises,  the  transmitted  murmurs  of  respiration,  and  the 
rhythmic  pulsation  of  the  aorta.5  These  sounds,  however, 
according  to  L.  Bernard,6  are  not  constant  over  the  abdominal 

164 


AUSCULTATION   OF   GASTROINTESTINAL   SOUNDS      165 

organs  nor  do  the  vibrations  heard  characteristically  in  the  healthy 
individual  alter  in  pathological  conditions.  Even  in  the  most 
recent  and  most  complete  treatises  on  auscultation,  the  only 
additional  statements,  so  far  as  the  gastro-enteric  tract  is  con- 
cerned, are  with  regard  to  the  rubbing  noises  audible  in  cases 
of  inflammation,  and  the  piping  notes  that  can  be  heard  when 
there  is  intestinal  stenosis.  Any  further  notice  of  the  facts  or 
possibilities  of  auscultation  of  the  stomach  and  intestines  during 
digestion  I  have  been  unable  to  find. 

As  anyone  can  easily  determine,  the  abdomen  is  not  poor  in 
noises  ;  on  the  contrary,  it  is  usually  much  richer  than  the  thorax, 
and  the  noises  are  of  the  most  diverse  character,  from  soft  gurg- 
lings to  loud  rumbling  explosions.  Any  special  attention  to  the 
peculiarities  of  certain  sounds  in  the  general  tumult  audible  at 
the  height  of  digestion  was  hardly  to  be  expected,  so  long  as  the 
nature  of  the  motor  activities  of  the  stomach  and  intestines  was 
not  well  understood.  The  recent  increase  of  our  knowledge  of 
these  activities,  however,  enables  us  to  recognize  more  accurately 
the  relation  between  the  movements  of  the  alimentary  canal  and 
the  sounds  these  movements  produce. 

The  most  characteristic  feature  of  the  movements  of  the 
stomach  and  intestines  is  without  doubt  rhythmicity.  Peri- 
staltic waves  pass  in  rhythmic  succession  over  the  gastric  vesti- 
bule, rhythmic  segmentation  kneads  the  contents  of  the  small 
intestine,  and  antiperistaltic  waves  rhythmically  follow  one 
another  in  the  proximal  colon. 

The  condition  most  favourable  for  the  production  of  sounds  in 
the  alimentary  canal  is  the  presence  of  a  gas  mixed  with  food 
more  or  less  fluid.  When  the  food  and  the  gas  are  churned 
together,  a  sound  must  result.  Air  in  fine  division  can  be  intro- 
duced into  the  stomach  by  eating  in  combination  with  other  food, 
or  by  themselves,  such  preparations  as  souffles,  light  omelettes, 
toast,  or  very  porous  bread.  I  have  also  used  a  thin  paste  of 
gluten-flour  and  milk,  thoroughly  stirred  with  white  of  egg  until 
the  mixture  was  frothy.  Eaten  with  a  little  cream  and  sugar, 
this  mixture  is  not  unpleasant.  These  preparations  should  not 
be  chewed  so  thoroughly  as  to  drive  much  of  the  air  from  the 
small  cells  in  which  it  lies  enclosed.  When  such  food  is  eaten, 
rhythmic  sounds  can  be  heard  over  the  pyloric  end  of  the  stomach, 
and  later  over  the  lower  quadrants  of  the  abdomen. 

In  listening  to  these  sounds  I  have  made  use  of  a  flat-disc 


166          THE   MECHANICAL   FACTOKS    OF   DIGESTION 

stethoscope,  with  the  metal  chamber  2  inches  in  diameter.  The 
flatness  and  weight  of  the  metal  chamber  render  it  so  stable  that 
it  remains  where  placed  without  being  held,  and  by  the  addition 
of  a  rubber  tube  of  sufficient  length  the  stethoscope  will  reach 
easily  to  any  situation  on  the  observer's  own  abdomen.  For 
several  months  I  kept  the  stethoscope  at  hand  near  my  bed,  and 
when  not  asleep  used  it  in  listening  to  the  sounds  of  digestion. 
At  times,  in  the  quiet  of  the  night,  it  is  possible  to  hear  the  sounds 
without  the  stethoscope.  Indeed,  the  vibrations  are  sometimes 
so  strong  that  they  can  be  felt  in  the  abdomen,  or  perceived  like 
the  tactile  fremitus  of  the  chest,  by  placing  the  hand  over  the 
region  in  which  the  sound  arises. 

The  rhythmic  sounds  are  not  due  to  respiration  ;  they  differ 
from  the  respiratory  murmurs  in  rate  and  time.  Nor  are  they 
due,  as  one  who  hears  the  confusion  for  the  first  time  might  sus- 
pect, to  the  chance  choice  of  a  rate  and  the  selection  of  such 
sounds  out  of  the  confusion  as  correspond  to  that  rate.  Graphic 
records  of  the  sounds  produced  by  the  stomach  and  small  intestine 
have  been  secured,  and  the  element  of  human  judgment  thereby 
eliminated.  In  registering  the  sounds  of  digestion  I  have  em- 
ployed the  first  method  used  by  Hiirthle7  to  register  the  heart- 
sounds.  A  telephone  transmitter,  rendered  specially  sensitive 
by  the  use  of  rather  coarse  carbon  granules  loosely  disposed,  was 
connected  in  series  with  five  dry  cells  (total  electro-motive  force 
5-5  volts)  to  the  primary  coil  of  an  inductorium.  The  secondary 
coil  of  the  inductorium  was  attached  to  platinum  electrodes  in  a 
moist  chamber.  Over  the  electrodes  lay  the  nerve  of  a  nerve- 
muscle  preparation.  The  contraction  of  the  muscle  raised  a  lever 
which  wrote  on  a  smoked  drum.  So  sensitive  was  this  arrange- 
ment that  ordinary  conversation  could  not  be  carried  on  near  the 
apparatus  without  marring  the  record.  Sound  vibrations  seem 
to  be  conducted  from  one  point  to  another  in  the  abdomen  much 
better  than  in  the  thorax.  But  when  sounds  not  arising  immedi- 
ately under  the  transmitter  caused  the  muscle  to  contract,  the 
recording  of  these  muffled  outlying  vibrations  could  be  largely 
avoided  by  withdrawing  the  secondary  coil  of  the  inductorium  to 
a  proper  distance.  In  order  that  the  observer  might  listen  to  the 
sounds  while  they  were  being  recorded,  a  telephone  receiver  was 
arranged  to  be  thrown  into  circuit  at  will. 

The  Sounds  produced  by  the  Stomach. — The  active  end  of  the 
stomach  is  the  pyloric  end.  The  food  in  the  vestibule,  as  we 


AUSCULTATION   OF   GASTROINTESTINAL  SOUNDS      167 

have  already  seen,  is  repeatedly  compressed  by  peristaltic  waves 
moving  up  to  the  pylorus.  If  the  sphincter  does  not  relax  as 
the  ring  of  constriction  approaches,  the  only  escape  for  the  food 
is  back  through  the  narrow  advancing  ring  (cf.  Fig.  4).  Since 
the  waves  are  recurring  with  rhythmic  regularity  and  the  pylorus 
relaxes  only  occasionally,  the  food  near  the  pylorus  must  be 
squeezed  and  regurgitated  by  wellnigh  every  constriction  ring. 

That  the  rhythmic  gastric  sound  is  caused  by  the  escape  of  the 
food  backward  through  the  narrow  moving  orifice  was  proved  by 
the  following  observation.  A  mixture  of  starch  paste,  white  of 
egg,  and  subnitrate  of  bismuth,  stirred  with  an  egg-beater  until 
frothy,  was  given  by  stomach-tube  to  a  cat.  The  cat's  hair  had 
been  cut  short  over  the  pyloric  region,  and  the  skin  wet  with 
water.  When  a  stethoscope  was  applied,  little  gurgling  explosions 
could  be  heard  at  intervals  of  about  thirteen  seconds.  The 
animal  was  then  examined  with  the  X  rays,  and  peristaltic  waves 
were  found  recurring  at  intervals  of  thirteen  or  fourteen  seconds. 
As  a  constriction  was  about  to  pass  up  to  the  pylorus,  the  noisy 
X-ray  machine  was  stopped,  and  the  stethoscope  applied.  At 
the  proper  time  the  characteristic  sound  occurred.  Meanwhile  no 
food  had  left  the  stomach ;  the  sounds  must  have  been  due  to 
the  regurgitation  of  the  food  through  the  advancing  peristaltic 
ring. 

Since  the  pyloric  end  of  the  stomach  reaches  farther  to  the 
right  than  any  other  part,  it  is  clear  that  by  reclining  on  the  left 
side  the  pyloric  end  will  be  brought  uppermost.  When  the 
stomach  is  so  situated,  the  lighter  food — i.e.,  food  mixed  with 
air — will  naturally  rise  into  the  pyloric  end.  Peristaltic  waves 
passing  over  this  somewhat  viscous  mixture  of  air  and  chymous 
food  will  then,  for  reasons  already  stated,  produce  audible 
vibrations.  Sounds  quite  distinct  when  a  subject  lay  on  his  left 
side  became  very  weak  or  inaudible  when  he  turned  so  that  the 
pyloric  end  was  lowermost. 

The  stomach-sounds  can  best  be  heard  after  a  fairly  bountiful 
meal  in  which  has  been  included  a  large  admixture  of  the  food 
of  spongy  consistency  already  mentioned.  The  subject  should 
lie  on  his  left  side.  The  disc  of  the  stethoscope  should  be  placed 
about  midway  between  the  umbilicus  and  the  lower  end  of  the 
sternum,  and  to  the  right  of  the  median  line.  Not  all  persons  I 
have  examined  have  exhibited  the  sounds.  When  the  sounds 
appear,  however,  they  are  usually  loud,  rattling,  explosive,  and 


168         THE  MECHANICAL  FACTORS   OF  DIGESTION 

of  a  characteristic  quality  quickly  recognized  after  they  have 
once  been  fixed  in  mind.  But  occasionally  there  is  only  the 
recurrence  of  a  short  series  of  pops.  In  some  individuals  the 
sounds  are  louder  and  more  distinct  than  they  are  in  others  ;  and 
in  all  the  cases  I  have  studied,  the  sounds,  even  within  two  or 
three  minutes,  have  varied  considerably  in  intensity.  At  times 
the  characteristic  explosive  discharges  last  several  seconds ;  at 
other  times  there  is  at  the  regular  period  merely  a  sharp,  short 
report.  Between  the  moments  when  the  typical  sounds  return, 
one  can  ordinarily  hear  with  more  or  less  distinctness  a  sudden 
little  pop,  and  perhaps  several,  always  coming  at  irregular 
intervals.  These  sharp  pops,  which  resemble  the  bursting  of 
bubbles,  can  be  heard  in  all  parts  of  the  abdomen,  but  with 
greatest  frequency  on  the  right  side. 

The  gastric  sound  recurs  approximately  every  twenty  seconds. 
In  one  individual  the  interval  was  usually  from  seventeen  to  nine- 
teen seconds  ;  in  another,  about  twenty-one  seconds  ;  and  in  a 
third,  about  twenty-four  seconds.  These  rates  vary,  as  the  rate  of 
gastric  peristalsis  in  the  cat  varies  (see  p.  54),  at  different  times 
in  the  same  individual.  In  the  first  case  mentioned  above,  for 
example,  the  interval  was  occasionally  twenty  and  twenty-one 
seconds.  In  all  lower  animals,  except  the  rabbit,  that  I  have 
examined  with  the  X  rays,  peristaltic  waves  have  been  found 
running  over  the  stomach  with  monotonous  regularity  whenever, 
during  gastric  digestion,  the  animal  has  been  observed.  In  man, 
also,  gastric  peristalsis  probably  runs  in  continuous  rhythm  until 
the  stomach  is  empty,  for  in  one  case  observation  during  the 
first  four  hours  after  a  meal  revealed  only  occasional  short  inter- 
ruptions of  the  rhythmic  sounds.  The  sounds  are  likely  to  be 
thus  interrupted  even  when  they  have  been  for  some  time  clearly 
and  regularly  audible.  The  silence  may  cover  one,  two,  or  even 
three  of  the  regular  periods.  It  is  noteworthy  that  when  the 
sound  can  be  heard  again  it  continues  the  previous  rhythm.  This 
fact  is  illustrated  by  the  following  figures,  showing  the  number  of 
seconds  between  successive  gastric  sounds  about  two  hours  after 
dinner  : 

19  20 

38=19+19  19 

18  19 

19  20 
59=19+20+20  38=19+19 
19  20 


AUSCULTATION  OF  GASTROINTESTINAL   SOUNDS      169 

The  equations  show  that  the  normal  periods  have  been  pre- 
served ;  the  peristaltic  rhythm,  therefore,  has  probably  been 
continuous  although  each  wave  has  not  produced  a  sound.  The 
sound  just  previous  to  a  silent  interval  is  likely,  in  my  experience, 
to  be  somewhat  louder  and  more  prolonged  than  is  usual.  This 
prolonged  sound  may  mean  a  discharge  of  food  through  the 
pylorus,  and  thereby  the  conditions  in  the  vestibule  may  be  so 
altered  that  the  immediately  succeeding  waves  can  cause  no 
sounds  until  the  region  is  again  normally  filled  ;  but  I  have  no 
evidence  of  this. 

Fig.  30  is  the  copy  of  a  record,  secured  by  the  telephone 
method  previously  described,  which  shows  graphically  many  of 
the  features  of  the  stomach-sounds  above  mentioned.  The 
different  heights  of  the  separate  marks  indicate  variations  in  the 
intensity  of  the  sounds.  The  duration  of  the  sounds  also  can  be 


FIG.  30. — GKAPHIC  RECORD  OF  THE  STOMACH  -  SOUNDS  SECURED  BY  PLACING 
OVER  THE  PYLORIC  REGION  A  TELEPHONE  TRANSMITTER  ACTIVATING  A 
NERVE-MUSCLE  PREPARATION. 

The  time  is  marked  in  intervals  of  ten  seconds. 

judged ;  for  example,  at  c  and  e  they  are  more  prolonged  than 
before  a.  One  of  the  intermediate  pop  sounds  is  recorded  at  a. 
Silent  intervals  are  indicated  in  the  regions  b,  d,  and/.  In  these 
regions  arrows  have  been  placed  at  the  points  where  the  sounds 
would  have  recorded  if  present.  The  regular  rhythm  is  resumed 
in  continuation  of  the  previous  rhythm.  The  silent  intervals  are 
not  always  so  frequent  as  this  record  shows  them ;  I  have  one 
tracing  in  which  the  marks  are  not  only  rhythmically  regular, 
but  of  almost  the  same  height,  uninterruptedly  for  fifteen  minutes. 
The  evidence  that  the  rhythmic  sounds  audible  over  the  pyloric 
region  are  due  to  the  rhythmic  recurrence  of  peristaltic  waves 
moving  up  to  the  pylorus  has  been  presented  in  a  comparison  of 
the  conditions  in  man  and  in  the  cat.  This  evidence  is  confirmed 
by  observations  of  Moritz  on  himself.  He  introduced  a  stomach- 
tube  into  the  pyloric  end  of  his  stomach,  and  found  that  there 
were  rhythmic  oscillations  of  the  intragastric  pressure  in  that 
region.  Examination  of  his  records  proves  that  the  rate  of 


170          THE   MECHANICAL   FACTORS    OF  DIGESTION 

gastric  peristalsis,  in  his  case  also,  is  approximately  three  waves 
per  minute,  or  waves  at  intervals  of  about  twenty  seconds.8 

Hertz  has  reported9  hearing  at  intervals  of  eighteen  and  twenty 
seconds  sounds  like  those  I  had  described.  In  one  case  he  states 
that  he  heard  "  a  series  of  short  pops  repeated  with  perfect 
regularity  every  seventeen  seconds  for  about  five  minutes."  In 
some  instances,  however,  Hertz  was  unable  to  hear  any  rhythmic 
sounds  arising  from  the  stomach,  an  observation  which  accords 
with  my  own  experience.  When  the  narrowness  of  the  peristaltic 
ring  of  the  vestibule  is  considered,  however,  the  securing  of 
reliable  auscultatory  evidence  of  gastric  movements  seems  not  an 
impossibility.  The  conditions  for  producing  vibrations  in  gastric 
contents  driven  through  the  narrow  ring  must  be  more  exactly 
determined. 

The  Sounds  produced  by  the  Small  Intestine. — Khythmic 
segmentation,  although  not  always  present,  is  by  far  the  most 
common  mechanical  process  to  be  observed  in  the  small  gut. 
The  segmenting  movements  have  a  more  rapid  rate  than  the 
stomach  movements.  In  the  cat  and  the  dog  rhythmic  con- 
tractions of  the  small  intestine  are  from  three  to  five  times  as 
frequent  as  the  waves  of  gastric  peristalsis. 

Usually,  on  listening  over  the  lower  abdomen,  especially  over 
the  right  lower  quadrant,  during  the  height  of  digestion,  the 
observer  hears  what  seems  at  first  only  a  great  confusion  of  noises. 
Without  experience  it  is  difficult  to  distinguish  in  the  midst  of 
this  tumult  the  rhythmic  sounds  of  the  small  intestine.  It  is 
well  to  listen  in  the  night  after  the  stomach  is  empty,  or,  better, 
an  hour  or  two  before  breakfast.  The  stomach  is  then  producing 
no  sounds,  and  the  active  part  of  the  large  intestine  can  be 
avoided  by  placing  the  disc  of  the  stethoscope  over  the  lower  left 
quadrant  of  the  abdomen.  As  already  mentioned,  these  sounds 
can  sometimes  be  heard  in  the  quiet  of  the  night  without  the  use 
of  the  stethoscope.  I  have  heard  them  thus,  and  determined 
their  rate  by  listening  at  the  same  time  to  a  clock  ticking  twice 
a  second. 

The  rhythmic  sound  of  the  small  intestine  is  different  in  quality 
from  the  gushing,  explosive  sound  of  the  stomach.  To  be  sure, 
the  intestinal  sound  is  not  always  the  same  :  sometimes  it  is  a  soft 
rustling  of  fine  crepitating  noises ;  sometimes  a  group  of  little 
rattling  explosive  discharges,  as  if  an  exaggerated  crepitation ; 
and  sometimes — as  heard  through  the  stethoscope — a  rough 


AUSCULTATION    OF   G  ASTRO -INTESTINAL   SOUNDS      171 

rolling  rumble,  like  miniature  thunder.  But  after  these  varia- 
tions in  quality  there  remain  three  features  of  the  intestinal 
sounds  that  are  fairly  distinctive.  First,  the  individual  sounds 
usually  rise  slowly  to  an  acme  of  intensity  and  then  gradually 
subside ;  but  they  may  increase  slowly  to  a  maximum  and 
suddenly  cease,  or  may  begin  loud  and  then  gently  decrease  to 
silence.  Thus  each  sound  may  last  two  or  three  seconds  or  more. 
The  second  characteristic  is  the  persistence  of  the  rhythm  for 
some  time  in  one  place  ;  it  may  be  audible  for  a  minute,  or  it  may 
last  for  many  minutes,  but  it  does  not  move  away  as  the  sound 
produced  by  a  peristaltic  wave  would  move.  The  third  feature 
is  the  distinctive  rate.  This  rate  is  usually  one  sound  every  seven 
or  eight  seconds,  but  I  have  heard  the  sounds  four  or  five  seconds 
apart,  and  at  times  ten  seconds  apart.  This  rate  would  occasion 
from  seven  to  twelve  movements  per  minute.  The  rhythmic 
contractions  of  the  small  intestine  are  thus  from  two  to  four  times 
as  frequent  as  the  waves  of  gastric  peristalsis,  a  ratio  correspond- 
ing to  that  in  the  cat  and  dog.  This  fact  and  the  fact  that  the 
rhythmic  sounds  can  at  times  be  heard  loudest  in  the  left  flank, 
far  from  the  active  ascending  colon,  have  led  me  to  regard  these 
sounds  as  a  result  of  the  activity  of  the  small  intestine  rather  than 
of  the  colon.  Of  course,  at  any  one  time  there  will  be  some 
variation  in  the  rate,  but  usually  it  is  not  great,  as  the  following 
figures,  showing  the  number  of  seconds  between  the  beginnings  of 
successive  sounds,  will  indicate  : 

8  8 

8  15  =  7  +  8 

6  9 

8  6 

13  =  7  +  6  9 

As  these  figures  illustrate,  the  sound  sometimes  skips  the 
regular  period,  but  continues  the  rhythm  on  reappearing. 

In  the  morning,  after  an  ample  dinner  the  evening  before,  I 
have  heard  these  rhythmic  sounds  continue  in  one  part  of  the 
abdomen  or  another  without  interruption,  for  more  than  an  hour 
and  a  half.  The  intestinal  sounds  are  not  peculiar  to  the  morning 
hours,  though  they  are  most  clearly  distinguishable  at  that 
time.  After  learning  their  qualities  and  rate,  I  have  heard  them 
distinctly  in  the  midst  of  active  digestion  in  the  afternoon  and 
evening.  Nor  are  they  peculiar  to  the  left  side  of  the  body.  At 
times  I  have  heard  them  loudest  on  the  right  side. 


172          THE   MECHANICAL   FACTOKS    OF  DIGESTION 

In  describing,  in  1902,  the  rhythmic  sounds  attending  rhythmic 
segmentation  in  a  cat  with  opened  abdomen,  I  stated  :  "  As 
new  rings  occurred  the  old  relaxed,  but  apparently  with  tardi- 
ness, for  the  contents  gurgled  as  if  forced  through  the  narrowed 
lumen."10  The  contraction  of  the  circular  muscle  at  fairly  regular 
intervals  along  the  length  of  a  mass  of  food  cuts  the  mass  into 
segments,  and  the  repeated  splitting  of  these  segments  to  form 
new  segments  must  bring  about  with  each  operation  a  squeezing 
and  shifting  of  the  food,  almost  simultaneously  along  the  whole 
extent.  If  the  food  contains  air,  the  squeezing  and  shifting  will 
result  in  audible  rumblings  and  crepitations.  The  presence  of 
valvulse  conniventes  conceivably  causes  the  sounds  to  be  louder 
than  they  would  be  in  a  smooth  intestine.  The  rather  long 
duration  of  these  sounds — sometimes  three  seconds  and  more — 
led  me  to  think  that  the  process  in  the  human  body  is  like  that 


FIG.  31. — GRAPHIC  EECORD  OF  THE  RHYTHMIC  SOUNDS  OF  THE  SMALL 
INTESTINE. 

The  height  of  the  records  has  been  reduced  to  one-fourth  the  original  size.      The 
time  is  marked  in  intervals  of  five  seconds. 

observable  in  the  cat  and  dog,  and  not  the  simple  to-and-fro 
oscillation  of  a  small  bit  of  food  observable  in  the  rabbit. 

These  observations,  made  in  1905,  have  not  yet  been  confirmed 
by  others.  In  1907,  Hertz  reported  his  failure  to  hear  rhythmic 
sounds  of  the  character  I  had  described.  He  succeeded,  however, 
in  observing  with  the  X  rays  rhythmic  segmentation  in  the 
human  small  intestine,  and  at  almost  exactly  the  rate  I  had  noted 
for  the  sounds  which  I  attributed  to  the  segmenting  move- 
ments (see  p.  133). 

The  subjective  element  in  the  auscultatory  evidence  for  these 
sounds  is  eliminated  when  they  are  made  to  record  themselves. 
Such  a  record,  secured  by  the  method  already  described,  is 
shown  in  Fig.  31.  It  is  a  record  of  sounds  heard  before  breakfast 
one  morning  about  9.30  o'clock.  The  dinner  at  6  o'clock  the 
previous  evening  consisted  of  grape-fruit,  mackerel,  potato, 
cucumber  and  tomato  salad,  four  slices  of  bread  and  butter,  and 
strawberries  and  cream  with  cocoanut  cakes.  About  10  o'clock 


AUSCULTATION   OF   GASTRO -INTESTINAL   SOUNDS      173 

in  the  evening  four  slices  of  bread  and  butter  and  a  glass  of  milk 
were  taken.  At  the  time  this  record  was  made  the  telephone 
transmitter  was  placed  on  the  lower  left  quadrant  of  the  abdomen. 
The  duration  of  the  sounds  is  not  indicated,  since  the  recording 
muscle  contracted  in  each  case  only  at  the  climax  of  intensity. 

The  Sounds  produced  by  the  Large  Intestine. — Antiperistaltic 
waves  moving  toward  the  caecum  must  press  the  food  into  a 
blind  pouch,  and  the  only  escape  for  the  food  must  be,  as  in  the 
stomach  with  the  pylorus  closed,  back  through  the  advancing  ring. 
Each  peristaltic  wave  should  produce  a  sound,  therefore,  similar 
in  quality  to  that  of  the  stomach.  From  the  analogy  of  the  cat 
and  dog,  one  would  expect  these  waves  to  have  about  the  same 
rate  of  recurrence  as  the  gastric  waves.  One  would  expect,  like- 
wise, that  they  would  run,  not  continuously,  like  the  gastric  waves, 
but  for  short  periods,  when  new  masses  of  food  enter  the  colon  from 
the  small  intestine ;  that  they  might  appear,  as  in  the  cat,  after  the 
injection  of  a  large  enema ;  and  that  during  the  periods  of  activity 
the  waves  would  follow  one  another  in  a  fairly  regular  rhythm. 

The  greater  activity  in  the  right  lower  quadrant  of  the  abdomen 
is  manifested  by  the  more  frequent  occurrence  of  sounds  there 
than  in  the  left  lower  quadrant.  At  times  an  almost  constant 
succession  of  little  popping  noises  and  faint  gurglings  can  be 
heard  in  the  region  over  the  ascending  colon  when  the  region  over 
the  descending  colon  is  quite  silent.  But  in  spite  of  listening 
in  the  region  of  the  caecum  for  hours,  at  different  times  of 
the  day,  and  with  my  body  in  various  positions,  a  uniform  and 
characteristic  rhythm  of  the  sounds  in  this  region,  if  it  be  present, 
has  escaped  me.  Sounds  of  a  coarse  rumbling  character,  some- 
what like  those  of  the  stomach  but  usually  more  prolonged,  are 
at  times  audible.  These  sounds  were  once  heard  recurring 
regularly  for  a  short  period  at  intervals  of  about  twenty  seconds. 
More  commonly,  in  my  experience,  such  irregular  intervals  as 
these — 45,  25,  35,  27,  25,  14,  and  29  seconds — are  observable. 
Inasmuch  as  these  sounds  are  not  clearly  rhythmic,  it  seems 
questionable  whether  they  are  produced  in  only  one  part  of  the 
intestine.  But  these  gurglings  are  heard  loudest  along  the 
ascending  and  transverse  colon,  and  for  that  reason  are  probably 
due  to  activities  of  the  large  bowel. 

The  absence  of  a  regular  rhythm  in  the  repeated  contractions 
of  the  large  intestine  has  been  supported  by  experience  with 
enemata.  The  enemata  consisted  of  starch  and  a  little  flour 


174          THE  MECHANICAL   FACTORS    OF  DIGESTION 

boiled  in  normal  salt  solution.  The  resulting  paste  was  thin,  yet 
viscid  enough  to  be  stirred  into  a  froth  much  like  soapsuds. 
Enemata  of  this  kind,  made  frothy,  were  introduced  at  body 
temperature  in  amounts  varying  between  1,500  c.c.  and  2,000  c.c. 
In  order  to  avoid  confusing  noises  from  the  stomach,  their  effects 
were  studied  in  the  morning  before  breakfasting,  and  they  were 
usually  preceded  by  a  cleansing  enema  of  warm  normal  salt 
solution.  If  the  body  is  kept  in  a  horizontal  position,  the  fluid 
can  be  retained  for  a  half -hour  or  more  without  difficulty.  During 
this  time,  especially  if  the  pelvis  is  raised,  there  are  repeated  pains 
or  cramps,  referred  most  commonly  to  the  region  of  the  hepatic 
flexure  of  the  colon.  Sometimes  the  pains  are  referred  also  to 
midway  in  the  transverse,  and  less  often  to  the  ascending  colon. 
They  are  very  distinct  and  quite  unmistakable  in  their  character. 
It  is  remarkable  that  these  recurring  cramps,  which  are  un- 
doubtedly due  to  contractions  of  the  intestine,  are  ordinarily  not 
felt  in  the  descending  colon,  sigmoid  flexure,  or  rectum,  but  are 
restricted  to  the  proximal  colon,  the  region  which,  in  the  lower 
animals,  is  characterized  by  the  greatest  activity. 

The  contractions  attending  the  pains  are  not  expulsive,  nor 
do  they  seem  to  move  backward  from  the  part  in  which  they  are 
felt,  for  no  sound  is  audible  over  the  csecum  either  during  the  pain 
in  the  hepatic  flexure  or  after  it  has  disappeared.  The  con- 
tractions apparently  occur  again  and  again  in  the  same  region 
without  moving  in  either  direction.  In  the  cat  I  have  observed 
such  repeated  circular  contractions  of  the  proximal  colon  (see 
p.  151),  but  they  are  not  usual. 

The  recurrent  pains  ordinarily  last  from  six  to  eight  seconds, 
increasing  gradually  in  intensity  until  just  before  the  end.  They 
are  commonly  attended  by  gurgling  noises  audible  as  the  cramp  is 
passing  away.  The  cramps  have  been  observed  succeeding  one 
another  for  nearly  ten  minutes  at  intervals  varying  between 
nineteen  and  twenty-two  seconds,  but  in  my  experience  they  are 
ordinarily  not  so  regular  as  this.  The  following  figures,  repre- 
senting in  seconds  the  time  between  the  onset  of  successive 
cramps,  illustrate  the  usual  rather  irregular  recurrence  of  the 
contractions : 

28          39  22  43 

47          35  15  42 

35          15  25  40 

15  50  43 

23          18  40  54 

41          35  25  37 


AUSCULTATION  OF   GASTKO-INTESTINAL  SOUNDS      175 

From  the  evidence  I  have  been  able  to  secure  by  auscultation 
and  from  sensations  of  cramp,  it  seems  certain  that  the  ascending 
and  first  part  of  the  transverse  colon  are  more  active  than  the  re- 
mainder of  the  large  intestine.  As  we  have  learned,  the  evidence 
for  antiperistalsis  in  this  more  active  region  is  not  conclusive.  I 
have  already  mentioned  that  Elliott  and  Barclay-Smith  found 
such  sacculation  as  occurs  in  the  human  colon  associated  with 
emphasized  churning  activity  of  the  walls  of  the  sacculi.  In  repeat- 
ing their  observations  on  the  guinea-pig  and  rabbit,  I  have  seen 
oscillating  movements  of  single  sacculi,  now  here,  now  there,  or  of 
many  sacculi  at  the  same  time,  each  contracting  repeatedly, 
squeezing  out  the  contents  of  the  pouch,  crowding  full  the  neigh- 
bouring pouches  which  in  turn  became  active,  then  relaxing, 
filling,  and  discharging,  again  and  again,  till  the  food  was 
thoroughly  churned.  Such  a  process  could  not  be  attended  by  a 
clearly  marked  rhythm  :  too  many  little  activities  are  going  on  at 
the  same  time.  But  these  little  activities  would  naturally  be 
attended  by  the  continuous  popping  noises  and  the  slight  gur- 
glings which  are  heard  at  times  over  the  ascending  colon.  Is  it 
not  likely  that  in  man,  even  though  antiperistalsis  may  occur 
in  the  proximal  colon,  oscillating  contractions  of  the  sacculi 
constitute  the  more  prominent  operation  ? 

Although  auscultation  has  failed  to  bring  evidence  of  antiperi- 
stalsis in  the  colon,  the  method,  as  used  by  Hertz,  has  served  to 
indicate  when  material  begins  to  pass  through  the  ileo-colic  valve. 
In  the  morning  before  breakfast  he  heard  nothing  over  the 
caecum.  The  silence  persisted  rntil  between  four  and  four  and  a 
half  hours  after  breakfast,  when  a  few  quite  characteristic  sounds 
were  heard,  which  became  louder  and  more  frequent  up  to  a 
maximum  from  one  to  two  and  a  half  hours  after  they  began. 
Then  confusions  of  sounds  occurred  because  of  the  taking  of  other 
meals.  The  first  caecal  sounds  were  found  by  the  X-ray  method 
to  coincide  with  the  first  appearance  of  a  shadow  in  the  caecum. 
They  seemed  to  be  produced  by  the  passage  of  fluid  contents 
through  the  ileo-colic  sphincter.  The  presence  of  gas  in  the  colon 
was  favourable  to  the  production  of  the  sounds,  for  they  decreased 
in  intensity  as  the  semi-fluid  material  accumulated.  In  auscul- 
tation, therefore,  we  have  a  means  of  determining  the  rate  of 
passage  of  material  through  the  small  intestine.11 

A  characteristic  sound,  not  periodic,  which  is  audible  at  times 
along  the  transverse  and  descending  colon  is  a  progression  of  little 


176          THE   MECHANICAL   FACTORS    OF  DIGESTION 

crackling  noises,  like  the  breaking  of  minute  bubbles.  The  sound 
starts  in  the  transverse  colon,  and  its  advance  can  be  clearly 
traced.  If  the  disc  of  the  stethoscope  lies  over  the  splenic  flexure, 
the  crackling  can  be  heard  first  faintly,  then  louder  and  louder, 
then  gradually  more  faintly  again ;  and  if  after  the  climax  of 
intensity  there  the  stethoscope  is  changed  to  a  position  farther 
along  the  large  intestine,  the  sound  can  again  be  heard  passing 
through  the  same  phases  as  before.  This  sound  is  likely  to  be 
followed  immediately  by  a  tendency  to  pass  gas  from  the  bowel. 
The  conveyance  of  gas  from  the  region  of  active  fermentation  in 
the  proximal  colon  to  a  place  from  which  it  can  be  finally  voided 
is  apparently,  therefore,  a  special  action,  and  conceivably  may 
occur  without  changing  the  position  of  the  firm  contents  of 
the  bowel. 

To  one  listening  for  the  first  time  for  rhythmic  abdominal 
sounds,  probably  the  most  striking  feature  of  what  he  hears  is  the 
large  number  of  sounds  which  are  not  rhythmic.  Most  prominent 
among  these  irregular  sounds  are  the  sudden  quick  discharges  or 
pops,  which  can  be  heard,  either  singly  or  in  a  short  series  of  three 
or  four,  almost  at  all  times  and  in  all  parts  of  the  abdomen,  though 
most  frequently  on  the  right  side.  As  already  stated,  these 
reports  resemble  the  sound  of  bursting  bubbles.  Occasionally  a 
continuous  little  gurgling  can  be  heard  for  some  moments, 
gradually  becoming  less  intense.  Peristalsis  in  the  small  intestine 
may  be  thus  manifested. 

A  noteworthy  characteristic  of  the  intestinal  sounds  is  their 
alteration  in  intensity  and  frequency  at  different  times.  I  have 
no  records  showing  this  variation,  but  it  has  impressed  itself  upon 
me  while  listening  for  long  periods  to  the  activities  of  the  intes- 
tines. At  times  there  will  be  almost  silence  in  the  lower  abdomen  ; 
the  silence  will  give  way  gradually  to  an  abundance  of  sounds, 
and  these  in  turn  will  subside  till  again  only  occasional  sounds  are 
audible.  The  observations  of  BoldirefE  have  proved  that  the 
alimentary  canal  has  a  periodic  activity  while  not  digesting  ;12 
the  intestines  may  also  have  alternating  periods  of  increased  and 
decreased  activity  while  digestion  is  going  on. 

Whether  the  observation  of  the  sounds  of  the  stomach  and 
intestines  is  to  be  of  clinical  importance  will  depend  on  whether 
there  are  typical  variations  of  these  sounds  in  different  diseases  of 
the  alimentary  canal.  The  observations  here  recorded,  made 
chiefly  upon  myself,  were  confirmed  on  a  few  other  normal 


AUSCULTATION   OF   GASTRO-INTESTINAL  SOUNDS      177 

individuals.  No  attempt  was  made  to  study  the  sounds  produced 
in  abnormal  conditions.  Irritation  in  the  region  of  the  ileo-colic 
junction  might  cause  reflex  spasm  of  the  sphincter  at  the  end  of 
the  small  intestine.  Material  would  then  cease  to  pass  into  the 
colon,  and  csecal  sounds  would  fail  to  appear.  Hertz  has  suggested 
that  the  presence  or  absence  of  these  sounds  would  be  serviceable 
in  differentiating  acute  appendicitis  with  and  without  peritonitis. 
In  cases  of  peritonitis  of  the  region,  he  found  that  the  sounds 
disappeared  as  the  inflammation  developed.13  Auscultation 
might  also  be  used  to  separate  the  somewhat  vague  expression 
"  motor  insufficiency  "  into  its  two  factors,  absence  of  peristalsis 
and  pyloric  obstruction.  Evidently  if  sounds  recur  in  regular 
rhythm  at  the  pylorus,  and  food  remains  in  the  stomach,  the  so- 
called  "motor  insufficiency"  is  due,  not  to  absence  of  peri- 
stalsis, but  to  difficulty  at  the  pylorus.  Furthermore,  in 
such  disorders  as  gastritis,  nervous  dyspepsia,  atony,  colic, 
obstruction,  and  dysentery,  a  study  of  the  sounds  produced 
by  the  movements  of  the  alimentary  canal,  both  before  and  after 
the  administration  of  drugs,  may  reveal  facts  important  to  the 
clinician. 

REFERENCES. 

1  Cannon,  Am.  J.  PhysioL,  1902,  vi.,  p.  259. 

2  Cannon,  Am.  J.  PhysioL,  1905,  xiv.,  p.  339. 

3  Hooke,   Posthumous  Works,   London,    1705,  The   Method  of  Improving 
Natural  Philosophy,  pp.  39,  40. 

4  Hooker,  Boston  M.  and  8.  J.,  1849,  xl.,  pp.  409,  439. 

5  See  Winkel,  Jahresb.  d.  Gesettsch.  f.  Natur-  und  Heilk.  in  Dresden,  Sitzung, 
December  6,  1873. 

6  Bernard,  L.,  Zur  Auscultation  des  Abdomens,  Inaugural-Diss.,  Wiirzburg, 
1879.     There  is  evidence  that  Bernard  is  mistaken  in  his  first  statement ;   he 
may  be  mistaken  also  in  his  second  statement. 

7  Hurthle,  Arch.  f.  d.  ges.  Physiol.,  1895,  lx.,  p.  264. 

8  Moritz,  Ztschr.  f.  Bid.,  1895,  xxxii.,  p.  353. 

9  Hertz,  Guy's  Hosp.  Rep.,  1907,  IxL,  p.  402. 

10  Cannon,  Am.  J.  PhysioL,  1902,  vi.,  p.  259. 

11  Hertz,  loc.  cit.,p.  412. 

12  Boldireff,  Arch,  des  Sc.  BioL,  1905,  xi.,  p.  1. 

13  Hertz,  Brit.  Med.  Jour.,  1908,  ii.,  p.  1603. 


12 


CHAPTER  XIV 

THE  INTRINSIC  INNERVATION  OF  THE  GASTROINTESTINAL 

TRACT 

THE  relative  parts  played  by  the  intrinsic  and  extrinsic  nerve- 
supply  of  the  gastro-intestinal  tract  can  perhaps  best  be  under- 
stood by  considering  first  the  activities  of  the  canal  separated 
from  the  central  nervous  system,  and  later  attending  to  the 
modifications  of  these  activities  through  external  connections. 
The  neuromuscular  mechanism  which  underlies  peristalsis  has 
been  studied  chiefly  in  the  small  intestine.  As  we  shall  see, 
probably  no  fundamental  difference  exists  between  the  intrinsic 
mechanism  in  the  small  intestine  and  that  elsewhere  in  the 
alimentary  canal.  The  peculiarities  of  the  activity  in  different 
parts  of  the  canal,  however,  make  desirable  a  separate  considera- 
tion of  each  part.  Thereafter  we  shall  be  in  a  position  to  deter- 
mine to  what  extent  a  general  statement  regarding  the  entire 
canal  is  justified. 

The  Small  Intestine. — Nothnagel  pointed  out  in  1882  that 
stimulation  of  the  rabbit's  small  intestine  with  a  crystal  of 
sodium  chloride  results  in  a  contraction  which  spreads  from  the 
stimulated  region  upward,  whereas  complete  rest  prevails  below.1 
After  persisting  for  a  variable  number  of  seconds,  the  contracted 
region  relaxes,  and  becomes  at  once  the  seat  of  peristalsis.  That 
contraction  occurs  above,  and  not  below  the  stimulated  region 
was  proved  also  by  Liideritz,  who  used  a  somewhat  more  natural 
method — the  introduction  of  an  inflatable  balloon — and  found 
that  rapid  distension  of  the  rabbit's  gut  caused  an  almost  exact 
repetition  of  the  phenomenon  described  by  Nothnagel.  When 
the  intestine  was  very  irritable,  the  balloon  was  driven  downward 
by  the  contraction  above  it,  and  thus,  by  successively  stimulating 
new  regions,  it  caused  a  downward-moving  peristaltic  wave. 
Since  these  results  occurred  after  the  nerves  in  the  mesentery 
were  cut,  Liideritz  concluded  that  the  controlling  mechanism 

178 


THE    INTRINSIC   INNERVATION  179 

must  be  present  in  the  intestinal  wall.2  The  modern  conception 
of  intestinal  peristalsis  was,  however,  not  fully  stated  until  Mall 
pointed  out  the  significance  of  Nothnagel's  observation  on  intus- 
susception. Nothnagel  had  reported  that  the  intussuscipiens  * 
portion  of  the  gut,  lying  below  the  point  of  stimulation,  folds  back, 
and  extends  upward  over  the  contracted  intussusceptum  lying 
above.3  Thus  contraction  above  and  relaxation  below  seemed 
so  related  as  to  be  parts  of  a  single  act.  And  Mall  concluded  that 
while  a  mass  in  the  intestine  is  causing  a  contraction  above,  which 
forces  the  mass  downward  and  thus  stimulates  fresh  regions 
above  to  contract,  active  dilatation  below  is  at  the  same  time 
inviting  an  easy  descent.4  Peristalsis  would  thus  be  another 
example  of  the  mutual  adjustment  of  antagonistic  muscles 
towards  efficient  action — an  example  which  presents  in  the 
simple  neuromusculature  of  the  gut  the  important  principles  long 
ago  perceived  by  Descartes  and  Bell  in  the  neuromusculature  of 
the  skeleton,  which  in  recent  years  have  been  named  by  Meltzer 
and  by  Sherrington,  respectively,  "  contrary  "  and  "  reciprocal  " 
innervation. 

Although  Nothnagel  and  Liideritz  had  shown  experimentally 
the  intrinsic  control  of  peristalsis,  and  Mall  had  clearly  inferred 
the  nature  of  the  peristaltic  wave,  Bayliss  and  Starling  made  the 
first  exact  demonstration  of  the  process.  When  they  introduced 
.a  bolus  into  the  dog's  intestine,  they  observed  the  formation  of  a 
"  strong  tonic  contraction  "  immediately  above  the  object,  which 
pressed  it  downward.  And  as  the  bolus  moved,  the  ring  of  con- 
striction followed  it.  The  region  of  the  gut  over  which  the  con- 
striction ring  had  just  passed  was  occupied  by  peristaltic  waves, 
which  repeatedly  swept  down  to  the  ring.  By  means  of  apparatus 
which  registered  the  movements  of  both  the  longitudinal  and  the 
circular  coats,  Bayliss  and  Starling  proved  that  the  descending 
bolus  was  preceded  by  an  area  of  relaxation.  The  two  effects, 
contraction  and  inhibition,  could  be  produced  by  pinching  the 
gut  above  and  below  the  recording  apparatus  ;  a  pinch  1  or  2  centi- 
metres below  caused  the  registering  of  an  increased  contraction  ; 
a  pinch  much  farther  above — even  30  centimetres  or  more — 
resulted  in  cessation  of  contraction  or  relaxation.  These  results 
appeared  after  exclusion  of  cerebrospinal  reflexes.  "  Excitation 
.at  any  point  of  the  gut  excites  contraction  above,  inhibition 
below.  This  is  the  law  of  the  intestine."  Such  was  the  con- 
clusion of  Bayliss  and  Starling.5  Since  this  co-ordinated  action 


180          THE   MECHANICAL   FACTOKS    OF  DIGESTION 

could  not  conceivably  be  performed  by  muscles  alone,  they 
inferred  that  it  was  controlled  by  Auerbach's  plexus,  possibly  by 
short  augmentor  paths  extending  upwards,  and  long  inhibitory 
paths  reaching  downwards. 

After  injecting  nicotine,  Bayliss  and  Starling  found  that 
rhythmic  contractions  of  a  stretched  ring  of  gut  continued,  but 
that  the  waves  of  constriction,  which  ran  over  the  gut,  now 
passed  as  often  in  one  direction  as  in  the  other.6  A  pinch  caused 
a  local  contraction  which  was  not  propagated  in  .either  direction  ; 
a  bolus  placed  anywhere  in  the  gut  remained  unmoved.  The 
same  results  followed  painting  the  intestine  with  cocaine,  or 
injecting  muscarine.  They  concluded  that  the  rhythmic  move- 
ments were  myogenic,  but  capable  of  travelling  as  a  wave  from 
muscle  fibre  to  muscle  fibre.  Usually  these  waves  moved  in  a 
downward  direction,  an  effect  which  they  suggested  might  result 
from  higher  excitability  at  the  duodenal  end.  True  peristalsis 
they  regarded  as  not  like  these  waves,  but  as  a  co-ordinated 
reflex,  consisting  of  combined  contraction  and  relaxation,  de- 
pendent on  the  proper  functioning  of  the  local  nervous  system.7 

More  detailed  work  on  the  functions  of  the  local  nervous 
system  of  the  intestine  was  done  by  Magnus,  and  has  been 
reported  in  a  series  of  valuable  papers.8  Using  0.  Cohnheim's. 
method,9  he  studied  excised  pieces  of  cat's  intestine,  kept  alive 
in  oxygenated,  warm  Ringer's  solution.  Thus,  Magnus  was 
able  to  secure  records  of  contraction  above  and  relaxation  below 
the  stimulated  point  in  isolated  loops  The  reflex  persisted  after 
removal  of  the  mucous  and  sub  mucous  layers,  including  Meissner's 
plexus.  It  is  therefore  mediated  through  Auerbach's  plexus — a 
conclusion  which  has  been  inferred  by  Bayliss  and  Starling. 

Bayliss  and  Starling's  evidence  that  the  rhythmic  contractions 
of  the  gut  are  myogenic  is  not  conclusive.  That  the  short  aug- 
mentor paths  and  the  long  inhibitory  paths  assumed  by  these 
investigators  are  in  fact  superintending  fibres  in  the  wall  of  the 
canal,  normally  affecting  subordinate  nervous  activities  in  a. 
positive  or  negative  manner,  is  easily  conceivable.  Indeed, 
Dogiel  has  found  histologically  that  an  axon,  on  leaving  a  ganglion, 
frequently  passes  through  several  neighbouring  or  more  remote 
ganglia,  and  gives  off  collaterals  to  the  nerve  cells  lying  in  them.10 
Nicotine  might,  then,  block  conduction  between  superintending 
and  subordinate  neurons,  and  still  leave  unaffected  the  subordi- 
nate  neurons. 


THE    INTRINSIC   INNERVATION  181 

Experimental  evidence  against  Bayliss  and  Starling's  con- 
clusion that  the  rhythmic  movements  are  myogenic  was  brought 
forward  by  Magnus.  His  first  argument  against  their  contention 
was  based  on  the  distinction  between  the  local  motor  centres  for 
muscular  action  and  the  conducting  paths  uniting  these  centres. 
He  had  found  in  the  marine  worm,  Sipunculus,  that  atropin 
paralyzes  conducting  paths,  but  not  the  centres,  whereas  cocaine 
paralyzes  the  motor  centres  before  stopping  conduction.11  It 
was  possible,  therefore,  that  the  drugs  used  by  Bayliss  and 
Starling,  although  destructive  to  the  machinery  of  the  local 
reflex,  did  not  seriously  injure  the  immediate  nerve-supply. 
The  rhythmic  contractions  therefore  might  result  from  rhythmic 
nervous  discharges. 

The  second  argument  of  Magnus  was  supported  by  more  direct 
proof.  He  found  that  when  the  longitudinal  and  circular 
muscular  layers  are  pulled  apart,  Auerbach's  plexus,  which  lies 
between,  adheres  to  the  longitudinal  layer.  Under  these  cir- 
cumstances the  longitudinal  muscle  alone  manifests  sponta- 
neous rhythmic  contractions.  The  circular  muscle,  deprived 
of  the  plexus,  although  capable  of  responding  to  a  single 
mechanical  stimulus  by  a  single  contraction,  never  shortens 
rhythmically. 

The  objection  has  been  raised12  that  the  circular  muscle  must 
be  seriously  injured  by  separation  from  the  longitudinal  coat  and 
the  nerve  net,  and  is  therefore  inert.  As  Magnus  has  pointed 
out,  however,  removal  of  the  submucosa  with  Meissner's  plexus 
is,  in  relation  to  the  circular  coat,  a  similar  operation,  but  it 
causes  no  alteration  of  the  activities  of  that  coat ;  and,  further- 
more, the  longitudinal  coat,  which  is  about  one-seventh  as  thick 
as  the  circular,  and  consequently  much  more  liable  to  injury, 
is  precisely  the  part  that  shows  the  peculiar  rhythmic  con- 
tractions.33 This  contention  of  Magnus  has  been  supported  by 
Sick,  who  succeeded  in  separating  from  the  stomach  pieces  of 
longitudinal  muscle  without  the  nerve  plexus,  and  in  observing 
that  they  then  no  longer  contracted  spontaneously.14 

According  to  Magnus's  careful  observations,  there  are  other 
important  differences  between  intestinal  muscle  when  controlled 
by  the  plexus  and  the  same  muscle  when  freed  from  that  control. 
The  independent  muscle  can  be  tetanized ;  it  gives  superposed 
contractions,  has  no  refractory  period,  and  manifests  no  rhythmic 
response  to  continued  stimulation.  On  the  other  hand,  good 


182          THE   MECHANICAL   FACTORS    OF  DIGESTION 

preparations  with  the  plexus  attached  cannot  be  tetanized,  are 
clearly  refractory  to  weak  stimulation  during  the  period  of 
shortening  and  the  first  part  of  the  period  of  relaxation,  and  with 
continued  stimulation  exhibit  rhythmic  contractions. 

Of  these  activities  of  smooth  muscle  connected  with  its 
intrinsic  nervous  system,  the  most  significant,  in  relation  to  bodily 
functions,  is  the  refractory  period.  Given  the  refractory  period, 
the  rhythmic  response  to  continued  stimulation  necessarily 
follows.  The  rhythmic  nature  of  many  of  the  activities  of  the 
alimentary  canal  might  thus  receive  explanation.  The  con- 
tention of  Schultz,15  that  Magnus's  "  refractory  period  "  was  due 
to  defective  methods  of  stimulation,  Magnus  has  met  by  repeating 
the  experiments  under  better  conditions,  and  finding  again  that 
weak  stimulation  does  not  affect  the  intestinal  neuromusculature 
while  it  is  contracting,  and  becomes  effective  again  only  gradually 
as  the  muscle  relaxes.16  Magnus  was  able  furthermore  to  show 
the  refractory  period  by  mechanical  stimulation  ;  by  this  method 
I  also  have  obtained  evidence  of  the  phenomenon,  and  can 
therefore  confirm  Magnus's  statement. 

The  question  now  arises  as  to  the  conditions  under  which  the 
two  typical  movements  of  the  small  intestine  appear.  The 
simplest  movement  to  explain  is  that  which  causes  segmentation. 
It  is  only  necessary  to  attach  a  writing  lever  to  a  narrow  ring  of 
the  intestine  to  secure  a  record  of  rhythmic  contractions.  The 
ring  may  be  only  a  few  millimetres  wide  ;  the  rhythmic  response 
therefore  is  local.  It  can  best  be  explained  as  a  resultant  of  the 
stretching.  This  mechanical  stimulation  causes  contraction  ;  as 
soon  as  the  contraction  begins,  the  ring  becomes  refractory,  and 
is  not  again  subject  to  the  stimulus  until  it  is  relaxing.  Thus 
the  constant  pull  results  in  a  rhythmic  response.  The  extent  and 
force  of  the  contractions  are  increased  within  limits  by  an  in- 
creased distending  force,  or,  if  absent,  they  may  be  induced  in 
the  same  way.17 

In  harmony  with  the  foregoing  explanation  is  Bayliss  and 
Starling's  observation  that  the  contractions  of  the  gut,  when  a 
distending  balloon  is  introduced,  are  most  marked  in  the  region 
of  greatest  tension.18  In  harmony  with  that  explanation  also  is 
the  observation  that,  as  a  mass  of  food  is  being  pushed  along  the 
gut,  the  back  end  is  likely  to  be  cut  off  by  a  constriction  ring 
(see  p.  137).  The  violent  segmenting  activity  in  cases  of  obstruc- 
tion (see  p.  141)  also  points  to  distension  of  the  gut  as  a  cause  of 


THE    INTRINSIC    INNERVATION  18S 

rhythmic  contractions.  Indeed,  rhythmic  segmentation  itself  is 
an  excellent  example  of  the  response  of  the  gut  to  stretching,  for 
the  contraction  occurs  each  time  in  the  bulging  region  about 
midway  between  two  previous  contractions.  Experimental  evi- 
dence to  the  same  effect  I  have  secured  by  seizing  the  active, 
exposed  intestine  between  the  fingers  at  two  points  a  few  centi- 
metres apart,  and  placing  the  enclosed  contents  under  pressure 
sufficient  to  distend  the  gut.  The  distension  was  followed  by  the 
contraction  of  a  narrow  ring  of  the  circular  coat ;  and  when  the 
finger  pressure  was  repeated  rhythmically,  as  rapidly  as  a  con- 
tracted ring  relaxed,  a  new  contraction  occurred,  not  where  one 
had  just  appeared,  but  in  a  fresh  region.  Now  here,  now  there, 
the  gut  responded  to  the  distending  contents,  a  shifting  perhaps 
associated  with  lessened  irritability  in  the  region  just  recovering 
from  activity.  Since  these  rings  of  constriction  press  the  mucosa 
into  the  midst  of  the  food,  the  requirement  of  fresh  neuro muscu- 
lature for  contraction  results,  of  course,  in  the  utilization  of  fresh 
mucosa  for  absorption. 

Why  peristalsis  of  the  small  intestine  starts  and  why  it  stops 
is  not  known.  Certainly  nutriment  is  not  pushed  onward  con- 
tinuously from  stomach  to  colon.  Even  in  the  active  small 
intestine  of  the  rabbit  the  food-masses  can  be  seen  in  different 
loops  lying  for  some  time  undisturbed  by  any  movement  of  the 
wall.  In  the  less  active  gut  of  the  cat  this  stasis  of  the  contents 
is  even  more  marked.  Yet  from  this  quiet  state,  or  even  after 
segmentation  has  been  for  some  time  in  process,  a  peristaltic 
wave  will  appear,  force  the  mass  forward  for  a  short  distance, 
and  then  stop.  Under  experimental  conditions  mechanical 
stimulation  will  cause  contraction  above  and  relaxation  below. 
Magnus,  for  example,  after  removal  of  all  the  mucous  lining  that 
normally  comes  in  contact  with  the  food,  could  still  demonstrate 
the  reflex  by  pinching.  But  the  reflex,  and  the  progression  of  the 
reflex  along  the  intestine,  are  not  the  same  phenomenon.  Peri- 
stalsis implies  an  advancing  wave,  and  although  food  containing 
cellulose  seems  to  be  carried  through  the  gut  rapidly  because  of 
the  mechanical  effects  induced  by  it,  nevertheless  the  chemical 
state  of  the  contents  is  probably  of  first  importance  for  the 
moving  contraction.  Bayliss  and  Starling  found  that  cotton 
coated  with  soft  soap  was  an  efficient  stimulus  for  peristalsis  of 
the  small  intestine.  Nothnagel  and  others  used  strong  salt 
solutions  to  evoke  it.  I  have  observed  energetic  peristalsis  after 


184         THE  MECHANICAL  FACTORS   OF  DIGESTION 

the  injection  of  soapy  enemata,  and  after  introducing  into  the 
lumen  of  the  gut  a  small  cylinder  of  alkaline  soap.  Meltzer  and 
Auer  produced  rushing  peristalsis  by  administering  drugs  in 
stimulating  and  depressing  combinations  ;  the  cathartics  are 
irritants  of  vegetable  origin,  or  salts  only  slightly  absorbable. 
Most  of  these  agencies  would  affect  the  gut  not  so  much  by 
distension  as  by  chemical  stimulation.  The  observation  of 
Bokai,19  that  products  of  decomposition — carbon  dioxide,  marsh- 
gas,  hydrogen  peroxide,  and  skatol — cause  powerful  movements 
of  both  the  small  and  large  intestines,  and  Koger's  testimony20 
that  peptones  and  glucose  stimulate  peristaltic  activity,  are  to 
the  same  effect.  If  we  consider,  furthermore,  the  other  functions 
of  the  small  intestine  which  peristalsis  subserves — the  functions 
of  further  digestion  and  absorption — then  the  forwarding  of  the 
chyme  seems  required,  not  because  the  chyme  is  bulky,  but 
rather  because  fresh  regions  for  digestion  and  absorption  are 
desirable.  In  an  orderly  mechanism,  therefore,  we  might 
reasonably  regard  the  degree  of  digestion,  or  the  status  of  the 
mucosa,  or  some  relation  between  these  two,  as  a  basis  for 
explaining  the  peculiarities  of  intestinal  peristalsis. 

That  some  regulatory  arrangement  for  the  advancement  of 
material  through  the  small  intestine  exists  is  suggested  by  the 
fact  that  the  different  foodstuffs  do  not  pass  through  the  small 
intestine  with  the  same  speed  (see  p.  145),  and  yet  when  the 
end  of  the  ileum  is  reached,  practically  all  of  the  serviceable 
stuff  is  absorbed.  The  work  of  London  and  his  associates  indi- 
cates also  that  foodstuffs  are  absorbed  at  different  rates  at 
different  parts  of  the  tube — meat  most  in  the  upper  part,  starch 
and  fat  most  in  the  lower  part21 — and  that  in  each  portion  of 
the  tract,  in  the  case  of  any  particular  food,  a  constant  per- 
centage amount  is  absorbed,  quite  independent  of  the  amount 
fed.22  Nutriment  when  given  in  small  bulk  (50  c.c.)  was  dis- 
tributed in  the  small  intestine  quite  as  it  was  when  given  in 
large  bulk  (500  c.c.),  so  that  the  entire  tract  is  forced  into  service.23 
These  results  can  best  be  explained,  I  believe,  as  a  response  of 
the  canal  to  the  nature  and  state  of  the  intestinal  contents, 
rather  than  as  a  response  to  mechanical  stretching.  In  this 
connection  the  control  of  the  sphincters  of  the  stomach  by 
chemical  agencies  is  perhaps  significant.  The  manner  in  which 
the  chemical  character  of  the  chyme  may  affect  intestinal  peri- 
stalsis, however,  is  still  quite  hypothetical,  and  the  whole  ques- 


THE    INTRINSIC    INNERVATION  185 

tion  will  require  much  more  investigation  before  a  decisive 
answer  can  be  given. 

Further  discussion  of  the  mechanisms  governing  segmentation 
and  peristalsis  in  the  small  intestine  will  be  necessary,  but  we 
shall  be  able  to  look  on  these  processes  from  a  new  point  of  view 
after  considering  the  intrinsic  nervous  control  in  the  large  intes- 
tine and  the  stomach. 

The  Large  Intestine. — The  same  region  in  the  colon  may  mani- 
fest both  peristalsis  and  antiperistalsis.  In  my  observations,24 
and  in  those  of  Elliott  and  Barclay- Smith,25  antiperistalsis 
was  seen  in  the  middle  and  distal  thirds  of  the  large  intestine, 
from  which  regions  the  contents  are  normally  driven  by  peri- 
stalsis. The  English  investigators  have  reported  further  that  in 
the  rat  the  proximal  colon,  which  is  commonly  worked  over  by 
antiperistaltic  waves,  exhibits  the  peristaltic  reflex  if  the  material 
it  receives,  instead  of  being  soft  and  moist,  is  stiff  and  dry. 

Since  the  antiperistaltic  waves  are  not  affected  by  large  doses 
of  nicotine,26  they  are  like  the  rhythmic  segmenting  movements 
of  the  small  intestine.  And  again  like  the  segmenting  move- 
ments, these  waves  not  only  utilize  the  same  muscles  as  the 
downward-moving  constrictions,  but,  if  we  may  transfer  Magnus's 
evidence  to  this  final  region,  they  probably  utilize  also  the  same 
intrinsic  nerve  centres  that  are  involved  in  the  local  reflex. 

The  local  reflex  in  the  large  intestine  was  first  demonstrated 
by  Bayliss  and  Starling.27  They  found,  by  using  the  methods 
employed  in  studying  the  small  intestine,  that  both  in  the  dog 
and  in  the  rabbit  pinching  above  the  recording  balloon  caused 
an  inhibition  of  the  activities  below,  and  pinching  below  caused 
contraction  above.  The  ascending  excitation  in  the  dog  and  the 
descending  inhibition  in  the  rabbit  were  more  difficult  to  demon- 
strate than  the  reciprocal  activities.  At  most  the  descending 
inhibition  in  the  rabbit  extended  not  more  than  2  or  3  centi- 
metres below  the  stimulated  spot.  In  both  dog  and  rabbit  the 
activity  of  the  local  mechanism  diminished  from  the  ileo-colic 
valve  to  the  anus,  thus  throwing  the  evacuation  of  the  distal 
colon  more  and  more  into  the  control  of  extrinsic  nerves.  The 
local  reflex  in  the  rabbit's  colon  Langley  and  Magnus  were  able 
to  demonstrate  after  degeneration  of  the  post-ganglionic  sympa- 
thetic fibres.28  That  the  cat's  colon  also  is  the  seat  of  the  co- 
ordinated reflex  was  shown  by  Elliott  and  Barclay- Smith,  who 
found  that  distension  in  the  middle  third  of  the  large  intestine 


186          THE   MECHANICAL   FACTOKS    OF  DIGESTION 

of  this  animal  causes  constriction  above  the  distended  area,  and 
relaxation  below.29 

Thus  far  I  have  used  the  terms  "  peristalsis  "  and  "  antiperi- 
stalsis,"  as  if  descriptive  of  the  same  activity,  and  merely 
opposed  in  direction.  The  only  difference  between  them  that 
has  been  suggested  is  the  failure  of  nicotine  to  stop  antiperistalsis, 
whereas  in  the  small  intestine  nicotine  at  once  abolishes  peri- 
stalsis and  the  reflex  on  which  that  activity  rests.  Antiperi- 
stalsis is  peculiar  in  a  number  of  other  ways,  however,  which 
clearly  distinguish  it  from  the  propulsive  wave. 

The  chief  peculiarity  of  antiperistalsis  is  the  absence  of  a 
region  of  inhibition  projected  before  the  moving  ring  of  con- 
striction. As"  a  result,  these  rings  continue  passing  over  the, 
proximal  colon  in  a  close  series,  each  succeeding  constriction 
never  checking  or  interfering  in  any  way  with  those  already 
started  and  progressing  before  it. 

A  second  and  important  characteristic  of  the  antiperistaltic 
waves  to  which  I  have  called  attention30  is  their  origin.  In  my 
first  paper  on  the  movements  of  the  intestine,  I  reported  that 
these  waves  were  seen  starting  from  the  "  nearest  tonic  constric- 
tion." 31  Elliott  and  Barclay-Smith  also  noted  that  the  waves 
began  at  "  the  anal  limit  of  a  distended  area,"  "  from  the  upper 
limits  of  a  ring  of  constriction,"  "  from  a  deep  constriction  which 
formed  and  remained  with  slight  oscillations  as  a  starting-point."32 
Although  we  reported  thus  our  observations,  we  did  not  realize 
the  significance  of  the  tonus  ring  as  th°,  source  of  antiperistalsis. 
By  producing  a  tonus  ring  in  the  proximal  colon,  however,  by  a 
pinch  or  by  applying  a  weak  solution  of  barium  chloride,  I  have 
been  able  to  cause  the  waves  to  appear  at  will.  By  making  the 
ring  at  the  caecum,  repeated  downward-running  waves  may  be 
set  going ;  by  making  a  new  ring  now  at  the  terminus  of  these 
waves,  reversed  waves  appear,  and  meet  the  downward  waves 
progressively  nearer  the  caecum  until  only  reversed  waves  are 
running.  Furthermore,  a  tonus  ring  made  midway  in  the 
proximal  colon  I  have  seen  giving  rise  to  repeated  waves  which 
passed  away  in  both  directions.33  The  origin  of  antiperistalsis, 
therefore,  is  the  tonus  ring. 

A  third  feature  of  antiperistaltic  activity  in  the  colon  is  its 
rhythmicity.  The  waves  appear  one  after  another  at  regular 
intervals.  These  rhythmic  waves  must  have  a  source  that  is 
rhythmically  active.  Careful  inspection  of  the  tonus  ring  shows 


THE    INTRINSIC    INNERVATION  187 

that  at  regular  intervals  it  pulsates.  Each  pulsation  sends  away 
a  ring  of  constriction. 

A  fourth  characteristic  of  this  antiperistalsis  is  its  dependence 
on  a  state  of  tension.  If  a  tube  is  tied  into  the  colon,  and  as 
fluid  is  introduced  a  tonus  ring  is  made,  antiperistaltic  waves  are 
usually  started  by  the  ring.  If  now  the  fluid  is  largely  with- 
drawn, the  waves  cease.  Reintroducing  the  fluid  starts  them 
again.  The  observation  that  antiperistalsis  begins  as  soon  as  new 
food  enters  the  colon  from  the  ileum,  and  Elliott  and  Barclay- 
Smith's  method  of  starting  the  waves  by  injecting  air  or  gruel, 
agree  completely  with  the  idea  that  distension  is  the  condition 
under  which  the  waves  originate. 

Mechanical  extension  has  long  been  known  as  the  most  efficient 
stimulus  for  bringing  smooth  muscle  into  activity.  The  exten- 
sion, however,  must  not  be  merely  the  elongation  of  non- elastic 
substance.  When  smooth  muscle  is  flaccid  or  already  much 
relaxed,  extension  calls  forth  no  response.  Only  when  shortened 
and  resilient — i.e.,  in  a  state  of  tonus — does  the  pull  evoke  con- 
traction. 

According  to  Schultz,34  smooth  muscle,  when  much  contracted, 
is  extended  more  by  a  given  weight  than  when  less  contracted 
and  loaded  with  the  same  weight.  The  tonus  ring  is  a  region 
contracted  more  than  the  neighbouring  regions.  We  may 
assume,  therefore,  that  at  the  tonus  ring  the  neuromusculature 
is  in  a  condition  especially  favourable  to  extension  by  any 
internal  pressure,  and,  further,  that  it  will  respond  to  extension 
by  contraction. 

In  thus  responding  to  an  extending  force,  the  smooth  muscle 
of  the  colon,  like  that  of  the  small  intestine,  is,  during  the  entire 
period  of  shortening,  relatively  refractory  to  stimulation.  It 
begins  again  to  be  subject  to  the  stimulus  just  after  reaching  its 
most  contracted  state — i.e.,  when  again  most  extensible.  Now, 
by  being  extended,  it  is  stimulated,  and  again  responds.  In 
explaining  the  rhythmic  pulsation  of  the  tonus  ring  in  response 
to  a  constant  pull,  therefore,  the  same  factors  are  involved  as 
in  the  rhythmic  contractions  of  the  small  intestine. 

The  movement  of  a  wave  of  constriction  from  the  pulsating 
ring  towards  the  csecum  can  best  be  regarded  as  another  instance 
of  the  passage  of  the  state  of  excitation  from  an  active  to  a  less 
active  region  in  a  simple  neuromuscular  structure — a  phenomenon 
which  v.  Uexkiill  has  so  frequently  observed  in  the  nerve  net 


188          THE   MECHANICAL   FACTORS    OF  DIGESTION 

of  invertebrates  that  he  has  based  upon  it  a  general  law.35  Thus 
would  be  explained  the  departure  of  waves  from  a  pulsating  ring 
backwards  or  forwards,  or  in  both  directions  simultaneously,  as 
described  above.  In  my  experience,  this  progress  of  a  wave  does 
not  occur  if  the  wall  expands  sharply  at  the  edge  of  the  ring. 
The  wall  must  taper  from  the  expanded  to  the  narrow  region 
before  the  pulsations  will  send  off  the  moving  constrictions.  It 
is  a  corollary  from  the  above  discussion  of  the  effect  of  extension 
on  contraction  that  the  expanded  region  must  itself  be  in  a 
condition  to  be  extended — i.e.,  possess  some  degree  of  tonus — in 
order  to  be  in  a  state  to  respond.  If  the  gut  is  quite  relaxed,  the 
arousing  of  antiperistaltic  waves  from  a  pulsating  ring  is  usually 
impossible. 

The  wave  departing  from  the  contracting  ring  leaves  a  refrac- 
tory region  behind,  and  is  itself  a  moving  refractory  state  of  the 
neuromusculature.  The  only  direction  in  which  the  wave  can 
make  progress,  therefore,  is  away  from  its  origin.  As  soon  as 
the  region  of  the  colon  next  to  the  ring  has  contracted,  it  begins 
to  relax.  Thus  between  moving  rings  of  constriction  are  moving 
regions  of  relaxation.  When  the  region  next  the  tonus  ring  is 
relaxed,  it  is,  of  course,  again  subject  to  an  impulse  coming  to  it 
from  the  pulsating  ring.  What  is  true  of  this  region  is  true  also 
of  all  regions  lying  beyond.  Thus,  just  as  in  cardiac  contraction 
the  pulsations  of  the  sinus  set  the  pace  for  the  rest  of  the  heart, 
so  here  in  ths  colon  the  pulsations  of  the  tonus  ring  determine 
the  rate  at  which  waves  shall  appear. 

A  tonic  constriction  is  itself  refractory  to  the  stimulus  that 
comes  to  it  in  the  form  of  a  constriction  wave.  My  own  observa- 
tions and  those  of  Elliott  and  Barclay-Smith  on  antiperistaltic 
waves  observable  between  the  natural  tonic  constrictions  of  the 
colon  illustrate  the  definite  boundary  set  by  the  state  of  tonus. 
The  blocking  of  the  waves  started  at  tonus  ring  b  by  the  nearly 
relaxed  ring  a  (Fig.  32)  offers  another  illustration  of  the  same 
fact. 

The  dependence  of  pulsations  on  an  adjustment  between  locally 
increased  tonus  and  the  internal  pressure  is  also  illustrated  in 
Fig.  32.  The  colon  is  filled  with  fluid  ;  ring  6,  which  is  deep,  is 
pulsating  and  sending  forth  waves ;  ring  a,  which  has  relaxed, 
no  longer  pulsates.  The  two  rings  are  exposed  to  approximately 
the  same  internal  pressure.  This  is  adequate  as  a  stimulus  for 
the  deeper  ring,  but  not  for  the  less  deep.  Under  such  circum- 


THE    INTRINSIC    INNERVATION 


189 


stances,  I  have  been  able  to  renew  rhythmic  activity  in  the 
quiet  ring  merely  by  increasing  the  internal  pressure.  In  all 
probability  this  is  what  occurs  when  new  food  enters  the  large 
intestine  from  the  ileum,  and  starts  a  fresh  series  of  antiperi- 
staltic  waves.  And  once  started,  the  waves  can  be  augmented 
by  increase  of  internal  pressure.  For  example,  if  they  are 
shallow  depressions,  they  can  be  made  much  deeper  by  a  series 
of  slight  momentary  pressures  on  the  gut,  which  cause  repeated 
slight  distensions  of  the  wall  where  the  waves  are  passing. 

The  precise  relation  between  the  degree  of  tonus  and  the 
internal  pressure,  which  results  in  rhythmic  contraction,  is 
difficult  to  define.  When 
a  tonus  ring  is  first  made, 
either  by  a  pinch  or  by 
applying  barium  chloride, 
it  is  a  deep  and  strong  con- 
traction, and  shows  no  evi- 
dence of  pulsations.  Only 
when  it  has  relaxed  to  some 
extent  does  it  begin  to  beat 
rhythmically.  On  the  other 
hand,  if  the  pressure  within 
is  sufficiently  increased,  the 
waves  moving  along  the 
gut  will  disappear,  and  then 
can  only  be  seen  again 
when  the  distension  is  re- 
duced. Both  the  tonus  and  the  distending  force,  therefore, 
can  be  too  great  for  rhythmic  action. 

From  the  foregoing  discussion  we  can  understand  that,  given 
the  state  of  tonus  and  a  locally  increased  tonic  contraction,  anti- 
peristalsis  of  the  colon  can  be  explained.  The  conditions  for  the 
establishment  of  tonus  rings,  however,  are  still  undetermined. 
Since  the  rings  persist  after  destruction  of  the  spinal  cord,  they 
must  be  maintained  by  the  gut  itself.  Henderson's  observation 
that  the  movements  of  the  alimentary  canal  appear  if  the  carbon 
dioxide  content  of  the  blood  is  kept  normal  or  increased36  can 
be  explained  as  due  to  the  well-known  effect  of  this  gas  in  aug- 
menting my  enteric  tonus.  Probably  both  the  general  tonic  state 
of  the  proximal  colon,  and  also  the  tonus  rings,  are  of  local  origin, 
and  possibly  directly  dependent  on  the  character  of  the  blood- 


Em.  32. — PHOTOGRAPH  OF  A  COLON  EX- 
POSED UNDER  WARM  SALT   SOLUTION. 

Tonus  ring  b  is  sending  forth  antiperistal- 
tic  waves,  which  are  stopped  by  the 
nearly  relaxed  tonus  ring  a. 


190         THE   MECHANICAL   FACTORS    OF   DIGESTION 

supply.  More  than  this  we  are  not  at  present  warranted  in 
saying. 

Just  as  we  were  not  able  to  determine  the  normal  occasion  for 
peristalsis  in  the  small  intestine,  so  likewise  we  are  ignorant  of 
what  causes  the  appearance  of  peristalsis  in  the  region  where 
antiperistalsis  usually  prevails.  As  already  stated,  change  in 
the  nature  of  the  contents  may  change  the  direction  of  the 
waves.  Magnus  has  found  that,  when  senna  is  mixed  with  the 
food,  it  causes  an  evacuation  as  soon  as  it  enters  the  colon.  He 
was  unable  to  note  the  occurrence  of  antiperistalsis  in  any  of  ten 
animals  thus  treated.37  Possibly,  as  seems  to  be  true  in  the 
small  intestine,  the  peristaltic  wave  of  the  colon  is  related  to 
other  activities  of  the  region,  and  is  reserved  for  pushing  onward 
waste  material  from  which  all  good  has  been  removed  or  which 
has  dried  and  hardened,  or  for  quick  discharge  of  irritant  and 
harmful  substances.  In  this  activity  the  mechanism  of  de- 
fsecation  is,  of  course,  a  distinct  aid.  This  mechanism,  however, 
will  be  considered  in  relation  to  the  extrinsic  inner vation. 

The  Stomach. — The  characteristic  activities  of  the  stomach,  so 
long  as  gastric  digestion  persists,  are  the  repeated  peristaltic  waves 
running  over  the  pyloric  end,  and  the  tonic  contraction  of  the 
cardiac  end.  The  fact  that  the  waves  of  the  stomach,  like  those 
of  the  colon,  follow  one  another  in  a  series  indicates  that  the 
extensive  forerunning  inhibition,  such  as  is  seen  in  the  dog's 
small  intestine,  is  absent.  Moreover,  when  nicotine  is  given, 
even  in  large  doses,  the  gastric  waves  are  not  stopped.38  The 
peristaltic  activity  of  the  stomach,  therefore,  is  by  this  evidence 
placed  in  the  same  class  with  antiperistalsis  of  the  colon  and  the 
segmenting  movements  of  the  small  intestine. 

The  first  waves  of  gastric  peristalsis  are  usually  seen  in  the 
pyloric  region ;  later  they  begin  nearer  the  cardiac  end.  This 
observation  proves  that  there  is  no  special  and  peculiar  region 
for  the  origin  of  the  waves.  Indeed,  I  have  recently  found  that 
by  gradually  increasing  intragastric  pressure  the  waves  can  be 
made  to  start  progressively  nearer  the  pylorus  ;  or,  as  the  pres- 
sure is  decreased,  step  by  step  nearer  the  fundus.  Our  con- 
sideration of  rhythmic  antiperistalsis  in  the  colon  has  shown 
that  the  waves  start  at  a  pulsating  ring.  In  the  stomach  also 
the  rhythmically  recurring  waves  must  have  a  rhythmically 
pulsating  source.  The  conditions  in  the  colon  indicate  further 
that  whether  a  ring  pulsates  or  not  depends  on  the  relation 


THE    INTRINSIC   INNERVATION 


191 


between  the  degree  of  tonus  and  internal  pressure.  The  same 
factors  I  have  found  operative  in  the  stomach.  If  the  resting 
organ  is  contracted,  the  introduction  of  fluid  at  once  starts 
peristaltic  waves  ;  if,  on  the  contrary,  the  organ  is  flaccid  and 
relaxed,  the  introduction  of  material  usually  has  no  effect. 

During  the  process  of  gastric  digestion  the  stomach  maintains 
its  contractions  with  a  considerable  tonic  tightening  always 
existent.  The  intragastric  pressure,  6  to  16  centimetres  of  water, 
is  a  measure  of  the  tonus  of  the  muscle.  If  while  intragastric 
pressure  is  being  recorded  the  animal  is  given  adrenalin,  the 
pressure  at  once  falls  to  zero.  Simultaneously  peristalsis  ceases, 
and  does  not  begin  again  until 
the  pressure  has  to  some 
extent  been  restored  (see 
Fig.  33). 

The  stomach  when  first 
filled  has  roughly  a  conical 
shape.  The  circumference  is 
large  at  the  cardiac  end,  and 
progressively  smaller  as  the 


t 


FIG.  33. — RECORDS  OF  INTRAGASTRIC 
PRESSURE  AND  THE  CONTRACTIONS 
OF  PYLORIC  END  OF  THE  STOMACH 
AFTER  GIVING  ADRENALIN. 

Peristalsis  of  the  pyloric  end  (upper 
curve)  begins  again  after  pressure 
(lower  curve)  has  begun  to  rise.  Time, 
half-minutes. 


pylorus  is  approached.  If 
the  contents  are  fluid  or  semi- 
fluid, and  are  subjected  to  the 
tension  of  the  gastric  muscu- 
lature, the  pressure  through- 
out the  contents  (gravity 
aside) will  be  uniform.  Every  unit  area  of  the  wall  will  be  support- 
ing the  same  pressure.  Obviously,  then,  a  circumference  of  given 
width  in  the  larger  cardiac  end  will  be  subjected  to  greater  total 
stress  than  a  circumference  of  equal  width  in  the  smaller  pyloric 
end.  Since  the  forces  in  the  inactive  stomach  are  in  equilibrium, 
however,  the  circular  muscle  of  the  cardiac  end  necessarily  has 
to  exert  stronger  tension  than  that  in  the  pyloric  end.  And, 
furthermore,  since  the  muscular  wall  of  the  cardiac  sac  is  thinner 
than  that  of  the  vestibule,  there  are  fewer  muscle  fibres  in  equal 
cross-sections.  The  greater  circumference  and  the  weaker  mus- 
culature both  tend  to  place  the  cardiac  region  at  a  disadvantage. 
The  tension  of  the  muscle  in  this  region  must  therefore  deter- 
mine the  pressure  in  the  stomach. 

With  the  conditions  of  pressure  and  tonus  in  the  stomach 
known,   how  can  gastric  peristalsis  be  explained  ?     There  is 


192         THE   MECHANICAL   FACTORS    OF   DIGESTION 

evidence  that  the  observations  already  reported  on  the  factors 
governing  activity  in  the  proximal  colon  can  be  applied  here. 
As  we  noted  in  considering  antiperistalsis  in  the  colon,  the 
internal  pressure  may  be  too  slight  to  evoke  a  response  in  the 
tonically  contracted  muscle,  or  it  may  be  too  great.  On  the 
basis  of  these  observations,  we  may  assume  that  at  first  the 
muscles  of  the  cardiac  end  are  too  much  distended  to  respond, 
and  that  those  of  the  pyloric  end  are  too  little  distended.  Be- 
tween the  large  cardiac  end  and  the  small  pyloric  end,  however, 
the  relations  of  internal  pressure  and  tonus  will  be  intermediate. 
At  some  point  the  relations  will  be  such  that  the  neuromuscula- 
ture  responds  by  contraction.  The  material  displaced  by  this 
contraction  is  probably  accommodated  in  the  cardiac  region 
where  the  weakest  muscles  are  working  against  greatest  obstacles. 
As  the  contracted  circumference  relaxes,  however,  the  tonic 
pressure  from  the  cardiac  end  again  stretches  the  ring.  Thus 
the  contraction  will  be  repeated  rhythmically  at  this  point,  for 
the  same  reasons  that  were  given  for  the  rhythmic  response  of 
the  small  intestine  and  the  colon. 

Each  pulsation  will  send  off  a  wave,  just  as  in  the  colon,  but 
this  wave  will  travel  only  towards  the  pylorus.  This  direction  is 
not  taken  because  antiperistaltic  waves  cannot  occur.  If  a  frog's 
stomach  is  distended  with  water,  tied  at  the  two  ends,  and 
removed  from  the  body,  peristaltic  or  antiperistaltic  waves  will 
run  over  it,  according  to  the  end  having  a  pulsating  tonus  ring. 
Similarly  in  the  cat :  a  tonus  ring  made  near  the  pylorus  will  send 
waves  backward  over  the  vestibule.*39  The  failure  of  peristalsis 
to  move  from  the  pulsating  ring  in  the  stomach  backwards  over 
the  cardiac  sac  is  due  to  the  sac  meeting  too  much  pressure  to- 
be  able  to  respond.  If  it  were  not  so,  it  would  itself  be  the  pul- 
sating region.  The  sac  therefore  exerts  only  a  tonic  grasp  on 
its  contents,  and  the  waves  move  only  towards  the  pylorus. 
Probably  the  greater  internal  pressure  in  the  vestibule  which 
results  from  peristalsis  is  a  factor  in  bringing  this  region,  where 
the  muscle  rings  are  small  and  the  muscles  themselves  are  strong, 
into  more  powerful  activity. 

In  harmony  with  the  preceding  argument  is  the  observation 
already  mentioned,  that,  when  peristaltic  waves  are  running  on 

*  I  have  never  seen  these  reverse  waves  traverse  the  conically-shaped 
mid-region,  though  reversal  over  the  more  tubular  mid-region  of  man  haa 
been  reported  in  clinical  cases  (Rautenberg,  Deutsches  Arch.  f.  klin.  Med.,  1903, 
Ixxvii.,  p.  308). 


THE   INTRINSIC   INNERVATION  193 

the  stomach,  their  place  of  origin  can  be  shifted  close  to  the 
vestibule  by  increasing  internal  pressure,  or  almost  to  the 
fundus  by  decreasing  that  pressure.  In  the  first  procedure  the 
overstretched  region  is  extended,  and  the  pulsating  circum- 
ference, having  to  meet  a  greater  distending  force,  is  moved  to 
a  region  where  the  muscles  are  stronger  and  in  a  smaller  ring. 
In  the  second  procedure  precisely  the  opposite  occurs — the 
muscles  of  the  cardiac  end,  gradually  less  stretched  beyond  their 
responding  power,  begin  to  contract,  and  in  consequence  the 
pulsatile  source  of  the  waves  is  moved  farther  towards  the  area 
of  weakest  musculature  and  largest  circumference. 

In  the  stomach,  as  in  the  colon,  a  local  neuromuscular  mechan- 
ism is  present  for  causing  a  contraction  above  the  stimulated 
region.  Evidence  for  this  conclusion  I  presented  in  1907,40  and 
by  use  of  chemical  instead  of  mechanical  stimulation  Sick  has 
obtained  results  leading  to  the  same  conclusion.41  Inhibition 
below  the  stimulated  point  is  either  very  slight  or  extends  only 
a  short  distance.  The  local  reflex  may  assure  the  origin  of 
gastric  waves  as  near  the  cardia  as  possible.  But  that  it  prob- 
ably has  little  effect  in  the  management  of  gastric  peristalsis  I 
have  shown  by  cutting  rings  through  both  muscular  coats  to  the 
submucous  connective  tissue,  thus  entirely  severing  Auerbach's 
plexus.  In  one  instance  six  rings  were  thus  cut  between  the 
cardiac  end  of  the  stomach  and  the  pylorus,  and  after  three 
weeks  the  waves  were  seen  passing  with  perfect  regularity,  much 
as  in  a  normal  stomach.  When  a  wave  approached  in  an  upper 
section,  it  stretched  the  muscles  in  the  next  lower  section,  and 
they  responded  by  contracting.  The  contraction  passed  on 
rather  than  back,  because  the  neuromusculature  above,  still  in 
the  active  phase,  was  refractory,42  whereas  that  below,  relaxed, 
was  ready  for  contraction  in  response  to  extension. 

As  the  stomach  empties,  the  mid- region  becomes  narrow  (see 
p.  49).  The  waves  then  originate  at  the  upper  end  of  this 
gastric  tube  at  a  tonus  ring  separating  the  tube  from  the  cardiac 
sac.  The  ring  forms  a  depression  which  has  been  repeatedly 
noted  in  X-ray  photographs  of  the  human  stomach,43  and  is 
observable  also  in  the  exposed  stomach  of  lower  animals.  X-ray 
workers  have  called  this  persistent  constriction  the  "  incisura 
cardiaca."  The  activity  of  the  deepened  ring  can  best  be  under- 
stood in  terms  of  the  activity  of  tonus  rings  in  the  large  intes- 
tine. Since  the  stomach  when  full  has  a  conical  shape,  the 

13 


194          THE   MECHANICAL   FACTORS    OF  DIGESTION 

formation  of  a  gastric  tube  of  fairly  uniform  diameter  requires  a 
greater  contraction  at  the  cardiac  end  than  at  the  pyloric  end. 
Because  the  cardiac  incisure,  at  the  extreme  cardiac  end  of  the 
tube,  is  therefore  more  contracted  than  any  other  part  of  the 
stomach,  it,  like  the  tonus  ring  in  the  colon,  is  probably  more 
easily  distended  than  any  other  part.  Distension  by  the  internal 
pressure  causes  the  ring  to  respond  rhythmically.  Each  con- 
traction sends  off  a  wave  towards  the  pylorus.  And  as  the  food 
is  forced  on  into  the  intestine  the  cardiac  sac,  by  tonically  pressing 
on  its  contents,  provides  more  material  for  the  waves,  while 
helping  to  maintain  the  internal  pressure  necessary  for  the  con- 
tinuance of  gastric  peristalsis.  Only  after  the  means  of  exercising 
internal  pressure — i.e.,  the  contents — have  disappeared  does  the 
peristalsis  normally  cease. 

The  origin  of  tonus  in  the  gastric  neuromusculature  we  shall 
consider  in  connection  with  the  extrinsic  innervation  of  the 
stomach.  The  continuance  of  the  tonic  state,  when  once  estab- 
lished, can  be  seen  in  the  excised  stomach.  I  have  tied  the 
digesting  stomach  at  the  two  ends,  removed  it  from  the  body, 
placed  it  in  warm  oxygenated  Ringer's  solution,  introduced  a 
glass  tube  which  rose  above  the  gastric  level,  and  observed  for 
a  half-hour  peristaltic  waves  passing  over  the  organ,  and  the 
contents  being  gradually  discharged  as  the  volume  diminished. 
Possibly  the  slow  decrease  in  size  (increase  in  tonic  contraction), 
especially  where  the  pulsations  occur,  is  due  to  the  "  contraction 
remainder "  of  smooth  muscle.  This  phenomenon,  to  which 
Schultz  has  called  special  attention,44  is  due  to  the  failure  of  the 
muscle  to  relax  fully  before  the  occurrence  of  another  contraction. 
Evidently,  if  such  a  remainder  were  left  as  a  heritage  to  each 
successive  shortening,  a  process  of  building  up  would  occur. 
The  muscles  would  become  more  and  more  contracted — i.e., 
the  circumference  of  the  stomach  would  be  slowly  diminished. 
The  possibility  (see  p.  60)  that  the  smaller  size  of  the  stomach 
is  the  result  of  the  muscle  fibres  slipping  by  one  another,  and 
rearranging  themselves  in  an  increased  number  of  layers,  should 
also  be  kept  in  mind.  For  the  present  we  must,  therefore, 
accept  the  facts  of  the  tonic  state,  though  we  are  unable  to  define 
exactly  its  nature. 

The  Myenteric  Reflex. — We  have  now  reviewed  the  activities  of 
the  stomach  and  intestines  in  relation  to  their  intrinsic  nervous 
control.  Each  of  these  regions,  and  the  oesophagus  as  well,45 


THE   INTRINSIC   INNERVATION  195 

possesses  an  intrinsic  arrangement  whereby  a  stimulus  causes 
a  contraction  above  and  a  relaxation  below.  The  relaxation 
below  may  be  extensive  and  marked,  as  in  the  small  intestine 
of  the  dog,  or  may  be  close  and  slight,  as  in  the  small  and  large 
intestine  of  the  rabbit,  and  in  the  stomach  and  oesophagus. 
We  have  seen  that  throughout  the  alimentary  canal  the  smooth 
muscle  is  disposed  in  an  outer  longitudinal  and  an  inner  circular 
coat,  with  Auerbach's  plexus  between.  In  the  new  nomencla- 
ture this  nerve  net  is  called  the  "  myenteric  plexus."  Since  the 
local  reflex,  which  acts,  as  we  have  seen,  in  the  cardiac  and 
pyloric  sphincters,  and  everywhere  else  in  the  wall  of  the  canal 
to  assure  orderly  progression  of  the  contents,  is  mediated  by  the 
myenteric  plexus,  I  have  suggested  that  it  be  called  the  "  myen- 
teric reflex."46 

Although  more  or  less  extensive  inhibition  below  a  stimulated 
point  is  characteristic  of  the  myenteric  reflex  in  the  small  intes- 
tine, abolishment  of  this  inhibition  by  nicotine  does  not  stop  the 
passage  of  rings  of  constriction  along  the  gut.  Such  rings  or 
"  waves  of  constriction  "  were  described  by  Bayliss  and  Starling 
as  moving  in  either  direction  regularly  and  powerfully  along  the 
intestine  after  the  administration  of  nicotine  had  destroyed  the 
local  reflex.  The  usual  source  of  the  rhythmic  waves  in  the  dog, 
they  found,  was  in  a  slight  persistent  "  ring  of  constriction  " 
immediately  above  the  dilating  balloon.47 

The  conditions  in  the  small  intestine  appear  to  be  true  also 
of  other  parts  of  the  canal.  Although  the  myenteric  reflex  is 
present  and  capable  of  taking  control  of  the  musculature,  yet 
it  is  not  always  in  control.  It  does  not  govern  the  rhythmic 
contractions  of  the  small  intestine,  the  rhythmic  peristalsis  and 
antiperistalsis  of  the  colon,  and  probably  not  the  rhythmic 
waves  of  the  stomach.  In  each  of  these  cases  there  is  no  exten- 
sive forerunning  inhibition.  The  source  of  the  moving  waves  is 
a  pulsating  tonus  ring,  and  from  this  ring  waves  can  pass  off  in 
either  direction.  For  these  activities  the  tonic  contraction  of 
the  wall  of  the  canal  is  all-important. 

REFERENCES. 

1  Nothnagel,  Arch.  /.  path.  Anat.,  1882,  Ixxxviii.,  p.  4. 

2  Liideritz,  Arch.  f.  path.  Anat.,  1889,  cxviii.,  p.  33. 

3  Nothnagel,  Beitr.  z.  Physid.  u.  Pathol.  d.  Darmes,  Berlin,  1884,  p.  48. 

4  Mall,  Johns  Hopkins  Hosp.  Rep.,  1896,  i.,  p.  71. 

5  Bayliss  and  Starling,  J.  Physiol.,  1899,  xxiv.,  p.  110 


196         THE   MECHANICAL  FACTORS   OF  DIGESTION 

6  Bayliss  and  Starling,  loc.  c',t.,  p.  115. 

7  Bayliss  and  Starling,  loc.  cit.,  p.  116. 

8  Magnus,  Arch.  f.  d.  ges.  Physid.,  1904,  cii.,  pp.  123,  349,  ciii.,  pp.  515, 
525  ;  1906,  cxi.,  p.  152. 

9  Cohnheim,  Ztschr.  /.  BioL,  1899,  xxxviii.,  p.  420. 

10  Dogiel,  Arch.  f.  Anat.,  1899,  Suppl.,  p.  137. 

11  Magnus,  Arch.  f.  exper.  Path.  u.  Pharmakd.,  1903,  i.,  pp.  97,  103. 

12  Lewandowsky,  Die  Functionen  des  Zentral-Nervensystems,  Jena,  1907,  p.  92. 

13  Magnus,  Ergeb.  d.  Physiol.,  1905,  vii.,  p.  45. 

14  Sick,  Deutsches  Arch.  f.  Uin.  Med.,  1908,  xcii.,  p.  422. 

15  Schultz,  Arch.  f.  Physid.,  1905,  Suppl.,  p.  23. 

16  Magnus,  loc.  cit.,  1906,  cxi.,  p.  152. 

17  Bayliss  and  Starling,  J.  Physiol.,  1899,  xxiv.,  p.  105. 

18  Bayliss  and  Starling,  J.  Physid.,  1901,  xxvi.,  p.  134. 

19  Bokai,  Arch.  /.  exper.  Pathol.  u.  Pharmakd.,  1887,  xxiii.,  p.  209;  xxiv., 
p.  166. 

20  Roger,  Compt.  rend.  Soc.  de  Bid.,  1905,  Ivii.,  p.  312. 

21  London  and  Sivre,  Ztschr.  f.  physiol.  Chem.,  1909,  lx.,  p.  201. 

22  London  and  Sandberg,  Ztschr.  f.  physid.  Chem.,  1908,  Ivi.,  p.  402. 

23  London  and  Dobrowolskaja,  Ztschr.  f.  physid.  Chem.,  1909,  lx.,  p.  273. 

24  Cannon,  Am.  J.  Physid.,  1902,  vi.,  p.  269. 

25  Elliott  and  Barclay-Smith,  J.  Physid.,  1904,  xxxi.,  p.  278. 

26  Elliott  and  Barclay-Smith,  loc.  cit.,  p.  304. 

27  Bayliss  and  Starling,  J.  Physid.,  1900,  xxvi.,  p.  107. 
23  Langley  and  Magnus,  /.  Physiol.,  1905,  xxxiii.,  p.  50. 

29  Elliott  and  Barclay-Smith,  loc.  cit.,  p.  281. 

30  Cannon,  Am.  J.  Physid.,  1909,  xxiii.,  p.  xxvii. 
si  Cannon,  Am.  J.  Physid.,  1902,  vi.,  p.  265. 

32  Elliott  and  Barclay-Smith,  loc.  cit.,  pp.  280,  281,  284,  285. 

33  Cannon,  Am.  J.  Physid.,  1909,  xxiii.,  p.  xxvii. 

34  Schultz,  Arch.  /.  Physiol.,  1903,  Suppl.,  p.  1. 

35  v.  Uexkiill,  Ergeb.  d.  Physid.,  1904,  III.2,  p.  1. 

36  Henderson,  Am.  J.  Physiol.,  1909,  xxiv.,  p.  70. 

37  Magnus,  Arch.  f.  d.  ges.  Physid.,  1908,  cxxii.,  p.  258. 

38  Cannon,  Am.  J.  Physid.,  1909,  xxiii.,  p.  xxvii. 

39  Cannon,  Am.  J.  Physid.,  1909,  xxiii.,  p.  xxvii. 

40  Cannon,  Am.  J.  Physid.,  1908,  xxi.,  p.  xx. 

41  Sick,  Deutsches  Arch.  f.  Uin.  Med.,  1908,  xcii.,  p.  431. 

42  Ducceschi,  Arch.  p.  la  Sc.  Med.,  1897,  xxi.,  p.  167. 

43  Kaestle,  Rieder  and  Rosenthal,  Arch.  Rontgen  Ray,  1910,  xv.,  pp.  21-24. 

44  Schultz,  loc.  cit.,  p.  124. 

45  Cannon,  Am.  J.  Physid.,  1908,  xxi.,  p.  xx. 

46  Cannon,  Am.  J.  Physid.,  1909,  xxiii.,  p.  xxvi. 

47  Bayliss  and  Starling,  J.  Physid.,  1899,  xxiv.,  pp.  104,  115. 


CHAPTER  XV 

THE  EXTRINSIC  INNERVATION  OF  THE  GASTRO-INTESTINAL 

TRACT 

THE  stomach  and  intestines  receive  their  extrinsic  innervation 
from  three  regions  of  the  central  nervous  system — from  the  bulb, 
from  the  sacral  cord,  and  from  the  thoracico-lumbar  origin  of  the 
sympathetic.  Both  the  bulbar  and  the  sacral  systems  of  nerves 
are  in  general  motor.  The  bulbar  system,  through  the  vagi, 
innervates  the  canal  from  the  oesophagus  to  the  end  of  the 
ileum,  diminishing  in  influence  as  it  descends  ;  the  sacral  system, 
starting  at  the  anal  end,  reaches  upwards  along  the  colon,  with 
diminishing  influence  as  it  ascends.  Opposed  to  these  two  motor 
systems  is  the  sympathetic,  distributed  to  the  same  areas  which 
they  innervate,  and  acting  in  the  main  to  inhibit  what  they 
stimulate.1  Through  these  opposed  systems  the  automatic 
activities  of  the  gastro-intestinal  tract  can  be  modified,  not,  to 
be  sure,  voluntarily,  but  to  an  important  degree  by  the  general 
bodily  state  and  by  emotional  conditions.  The  way  in  which 
the  extrinsic  nerves  produce  their  effects  we  shall  consider  in 
relation  to  the  different  parts  of  the  canal — the  stomach,  small 
and  large  intestine — taken  separately. 

The  Extrinsic  Innervation  of  the  Stomach. — Connecting  the 
bulb  with  the  stomach  are  the  two  vagus  nerves.  Only  one  is 
required  to  give  the  entire  surface  of  the  stomach  a  motor  supply. 
Ducceschi  has  shown  that  this  fact  is  not  due  to  the  transmission 
of  impulses  through  the  myenteric  plexus ;  for  if  one  of  the  vagus 
trunks  is  cut  at  the  cardia,  the  corresponding  part  of  the  stomach 
does  not  respond  to  vagus  stimulation.  The  capacity  of  one  of 
the  cervical  vagi  to  innervate  the  whole  stomach  is,  therefore, 
probably  due  to  the  interweaving  of  fibres  from  the  two  nerves 
in  their  course  down  the  oesophagus.2 

The  vagus  fibres  distributed  to  the  heart  connect  with  the 

197 


198          THE   MECHANICAL   FACTORS    OF   DIGESTION 

intrinsic  nerve  cells  of  that  organ,  and  the  connection  is  readily 
interrupted  by  nicotine.  Although  the  endings  of  the  vagus 
fibres  in  the  stomach  have  not  been  traced,  probably  they  do 
not  impinge  directly  on  the  smooth  muscle,  but  affect  it  through 
nerve  cells  embedded  in  the  gastric  wall.  The  observation  of 
Bayliss  and  Starling,  that  nicotine  permanently  abolishes  the 
action  of  vagus  impulses  on  the  gut,3  may  be  interpreted  in  this 
manner.  For  reasons  which  we  shall  consider  in  discussing  the 
innervation  of  the  colon,  Langley  is  inclined  to  believe  that  these 
outlying  nerve  cells  are  not  part  of  the  my  enteric  plexus.4 

The  action  of  the  vagus  impulses  can  be  shown  by  recording 
alterations  of  gastric  pressure  as  a  result  of  vagus  stimulation. 
The  first  effect  of  moderate  stimulation  is  a  lessening  of  the  tonus 
of  the  muscle.  The  cardiac  sac  markedly  relaxes ;  and  although 
the  pyloric  waves  may  continue,  they  are  diminished  in  ampli- 
tude. The  inhibitory  action  may  last  in  some  instances  during 
sixty  or  seventy  seconds  of  stimulation ;  in  other  instances  it 
continues  only  ten  or  fifteen  seconds.  The  inhibition  is  followed 
by  an  augmentor  effect  indicated  by  increased  tonus  and  greater 
amplitude  of  the  rhythmic  waves  than  normal.  This  stage  in 
turn  is  followed  by  the  subsidence  of  both  tonus  and  waves  to 
the  initial  state.  When  a  vagus  nerve  is  repeatedly  stimulated, 
however,  the  tonus  increases  more  permanently  after  each  stimu- 
lation, and  in  some  instances  may  remain  continuously  high.5 
The  bulbar  supply,  therefore,  may  have  not  only  an  augmentor, 
but  also  an  inhibitory  effect,  and  the  evidence  from  stimulation 
indicates  that  the  inhibitory  effect  appears  after  a  shorter  latent 
period,  and  has  less  permanence  than  the  augmentor. 

The  function  of  the  vagus  impulses  can  be  inferred  also  from 
the  effects  of  severing  the  nerves.  These  effects  have  been 
studied  in  a  series  of  experiments  by  means  of  the  X  rays.6  The 
right  vagus  was  severed  below  the  origin  of  the  recurrent  laryngeal 
branch,  and  in  a  second  operation  the  left  nerve  was  severed  in 
the  neck.  When  both  nerves  were  thus  sectioned,  the  first 
effect  was  often  total  suppression  of  peristalsis.  In  two  instances 
in  which  the  second  vagus  was  cut  immediately  after  the  animals 
had  voluntarily  eaten  boiled  lean  beef,  no  gastric  peristalsis  was 
observed  for  four  hours ;  and  in  another  instance  in  which  this 
operation  was  done  the  day  previous,  no  gastric  peristalsis  was 
seen  during  the  first  three  hours  after  feeding.  This  depression 
of  function  was  observed  also  when  the  splanchnic  nerves  had 


THE   EXTRINSIC    INNERVATION  199 

been  previously  severed.  In  every  instance  of  vagus  section, 
however,  the  peristaltic  waves,  even  when  restored  and  running 
with  normal  rhythm,  were  characterized  at  first  by  being  extra- 
ordinarily shallow.  Sometimes  they  were  hardly  visible ;  at  other 
times  they  could  be  seen  distinctly  only  on  the  vestibule.  But 
the  period  during  which  the  movements  of  the  stomach  were 
late  in  commencing  and  were  notably  weak  did  not  long  con- 
tinue. As  days  passed,  these  abnormalities  largely  disappeared, 
and  the  waves  started  at  the  usual  time  and  had  much  of  their 
normal  vigour. 

The  similarity  between  the  effects  of  vagus  section  on  the 
stomach  and  on  the  oesophagus  is  noteworthy.  As  we  have 
learned  (see  p.  28),  the  immediate  effect  on  the  oesophagus  of 
severing  the  vagi  is  paralysis.  The  food  stagnates  in  the 
tube  for  hours,  distending  its  walls,  but  the  toneless  structures 
make  no  response.  In  time  the  part  composed  of  smooth  muscle 
recovers  its  power.  Then  distension,  it  will  be  recalled,  becomes 
the  efficient  stimulus.  At  first,  however,  a  slender  mass  has  no 
effect ;  the  addition  of  a  second  mass  is  required  to  call  forth  a 
constriction.  As  time  goes  on,  however,  even  a  slender  mass 
becomes  effective.  The  neuromusculature  has  recovered  by 
itself  the  state  which  the  vagi  formerly  maintained — the  tonic 
state  which  makes  it  resilient  when  stretched. 

That  the  restoration  observed  in  the  oesophagus  is  duplicated 
in  the  stomach  is  shown  by  what  occurs  when  all  extrinsic  nerves 
are  cut.  The  stomach  develops  in  itself  a  remarkable  degree  of 
tonus.  As  I  pointed  out  in  1906,  the  diameter  of  the  organ  in 
the  cat  may  under  these  circumstances  be  only  1-5  or  2  centi- 
metres— a  smallness  of  size  almost  incredible.7 

We  are  now  in  a  position  to  consider  the  normal  function  of 
the  vagus  nerves  with  reference  to  the  musculature  of  the 
stomach.  We  have  seen  that  repeated  stimulation  of  these 
nerves  causes  an  increased  and  more  permanent  tonic  contraction 
of  the  gastric  wall,  and  that  as  the  tonus  increases  the  peristaltic 
constrictions  increase,  and  vice  versa.  We  have  seen  also  that 
when  the  nerves  are  cut  the  activities  are  for  some  time  in  abey- 
ance, and  even  when  peristalsis  reappears  the  constrictions  at 
first  are  shallow.  We  may  conclude,  therefore,  that  the  function 
of  the  vagi  is  that  of  setting  the  muscles  in  a  tonic  state,  of 
making  them  exert  a  tension,  so  that  in  relation  to  the  gastric 
contents  thev  are  as  if  stretched  by  those  contents. 


200         THE  MECHANICAL  FACTORS   OF  DIGESTION 

The  prime  importance  of  the  tonic  state  for  normal  functioning 
of  the  gastric  neuromusculature  has  already  been  emphasized 
in  the  discussion  of  intrinsic  innervation.  The  evidence  there 
adduced  is  strengthened  by  the  observation  that,  when  all 
extrinsic  nerves  are  cut,  the  oesophagus  and  the  stomach  develop 
in  themselves  a  tonic  state.  Whether  the  extrinsic  nerves  are 
present  or  not,  the  muscles  of  the  gastric  wall  must  be  in  tonus, 
and  must  be  placed  in  tension  by  the  contents  before  response 
will  occur.  In  all  probability  the  extrinsic  nerves  (the  vagi) 
adapt  the  size  of  the  organ  to  the  varying  amount  of  food  taken 
in.  Thus,  if  the  stomach  were  relaxed,  these  nerves  might  set 
the  muscles  into  tension  about  a  small  amount  of  food  which 
otherwise  would  not  produce  any  tension  whatever.  After  these 
nerves  are  severed,  however,  the  intrinsic  tonus  which  appears 
compensates  by  rendering  the  stomach  so  contracted  that,  even 
if  only  a  small  amount  is  swallowed,  the  muscles  are  stretched, 
and  peristaltic  activities  are  at  once  started. 

The  question  now  arises  as  to  the  stage  in  the  digestive  process 
at  which  the  vagus  influences  affect  gastric  tonus.  That  during 
the  mastication  and  ingestion  of  food  impulses  pass  down  these 
nerves  to  the  stomach  was  proved  by  Pawlow's  observations  on 
the  psychic  secretion  of  the  gastric  juice.8  As  already  stated, 
repeated  stimulation  of  the  vagi  results  in  an  increased  tonic 
state,  which  is  much  more  persistent  than  that  which  follows 
single  stimulation.  Since  a  tonic  state  is  necessary  for  gastric 
peristalsis,  and  since  peristalsis  does  not  appear  if  the  vagi  are 
cut  shortly  before  the  ingestion  of  food,  the  inference  is  sug- 
gested that  just  as  there  is  psychic  secretion,  so  likewise  there 
is  psychic  tonus.  At  present,  however,  no  direct  evidence  has 
been. secured  for  this  inference. 

After  digestion  is  well  started,  the  vagus  nerves  can  be  severed 
without  altering  either  the  nature  of  gastric  peristalsis  or  the 
rate  at  which  the  stomach  empties  itself.  This  statement  is 
supported  both  by  observations  with  the  X  rays,  and  by  inspec- 
tion and  records  of  intragastric  pressure  when  the  digesting 
stomach  was  exposed  under  salt  solution.  Psychic  tonus,  like 
psychic  secretion,  would  be  aroused  while  food  was  being  ingested, 
and  might  continue  for  a  period  of  some  minutes  thereafter. 
Then  the  tonic  state  must  be  continued  by  other  agencies.  As 
the  above  evidence  and  also  observations  on  the  excised  stomach 
show  (see  p.  194),  the  tonic  state,  once  established  at  the  be- 


THE   EXTRINSIC   INNERVATION  201 

ginning  of  gastric  digestion,  is  self-supporting,  and,  again  like 
the  psychic  secretion,  maintains  itself  by  some  local  mechanism. 

The  inhibitory  impulses  along  the  vagi  have  their  function 
after  gastric  tonus  has  developed  a  considerable  pressure  in  the 
stomach.  By  introducing  a  balloon  into  the  cardiac  end  of  the 
stomach  through  an  oesophagotomy  opening  in  the  neck,  the 
alterations  of  intragastric  pressure  and  volume  can  be  recorded. 
If  now  the  animal  swallows,  the  food  does  not  pass  down  the 
03sophagus,  but  emerges  through  the  upper  opening.  Using  this 
method,  C.  W.  Lieb  and  I  have  shown9  that  after  each  separate 
swallow  intragastric  pressure  drops  almost  to  zero ;  and  if  the 
balloon  pressure  is  3  or  4  centimetres  of  water,  the  volume  of  the 
stomach  may  increase  by  8  or  10  c.c.  The  fall  of  pressure  begins 
between  two  and  five  seconds  after  the  larynx  rises,  and  the 
greatest  volume  change  is  reached  between  six  and  ten  seconds 
after  the  bolus  leaves  the  mouth.  The  admirable  character  of 
this  receptive  relaxation  of  the  stomach  can  be  appreciated  if 
we  recall  that  the  time  required  for  a  bolus  to  be  carried  through 
the  cat's  oesophagus  varies  between  seven  and  ten  seconds. 
Thus,  whenever  a  tonic  state  of  the  gastric  musculature  has 
raised  intragastric  pressure,  an  automatic  mechanism  exists  for 
lowering  that  pressure  while  the  oesophagus  is  pushing  new  food 
into  the  stomach.  If  the  vagi  are  cut,  the  phenomenon  does 
not  occur.* 

Stimulation  of  the  splanchnic  nerves,  most  observers  have 
reported,  causes  diminished  tonus  of  the  gastric  musculature  and 
weakening  of  the  rhythmic  contractions.  Again  we  note  the 
concomitant  variation  of  tonus  and  rhythmic  response  to  tension. 
A  maximum  loss  of  tone  and  total  disappearance  of  pulsations 
and  peristalsis  occur  when  adrenalin  is  administered  (see  Fig.  33, 
p.  191).  The  presence  and  action  of  inhibitory  sympathetic 
nerves10  was  thus  demonstrated  by  Elliott.  That  these  nerves 
exert  a  constant  influence  is  made  probable  by  the  observation 
that,  when  all  extrinsic  nerves  to  the  stomach  are  cut,  gastric 
peristalsis  and  the  rate  at  which  the  stomach  empties  are  more 
nearly  normal  than  when  the  vagi  alone  are  cut,  and  the  splanch- 
nics  left  intact.  The  abnormality  of  functioning  after  vagus 

*  The  recent  observation  by  Joseph  and  Meltzer  (Am.  J.  Physid.,  1911, 
xxvii.,  p.  xxxi),  that  in  the  rabbit  contraction  of  the  pyloric  portion  of  the 
stomach  is  accompanied  by  inhibition  of  duodenal  contractions,  may  be  a 
phenomenon  similar  to  the  receptive  relaxation  of  the  stomach.  Tho 
mechanism  of  the  duodenal  inhibition  has  not  been  reported. 


202         THE    MECHANICAL   FACTORS    OF  DIGESTION 

section,  therefore,  is  due,  not  only  to  the  absence  of  vagus 
impulses,  but  also  in  part  to  the  depressive  effect  of  the 
splanchnics.11 

Whether  sensory  impressions  arise  in  the  stomach  itself  is  still 
in  question.  From  clinical  experience,  surgeons  have  reported 
that  the  stomach,  and  the  intestine  also,  can  be  cut,  crushed,  or 
burned,  in  operations  on  the  conscious  human  subject  without 
any  experience  of  discomfort.  According  to  Lennander's  studies, 
no  sensations  of  pain,  touch,  heat,  or  cold,  arise  in  the  viscera  of 
the  abdomen  which  are  innervated  only  by  the  vagi  and  the 
sympathetic  nerves.  This  is  true  either  in  normal  conditions  or 
during  inflammation.  The  pain  not  infrequently  referred  to  the 
abdomen  is  explained  as  the  result  of  disturbances  in  the  serous 
membrane  and  the  subserous  connective  tissue  of  the  abdominal 
wall,  which  are  innervated  by  the  phrenic,  the  lower  six  inter- 
costal, the  lumbar  and  sacral  nerves.  This  parietal  surface,  like 
the  cornea,  seems,  when  stimulated,  to  originate  only  sensations 
of  pain.  It  may  be  stimulated  by  rubbing,  especially  when 
inflamed,  or  by  stretching  any  mesenteric  attachment  or  patho- 
logical adhesion  between  the  viscera  and  the  abdominal  wall.12 

In  support  of  the  contention  that  the  abdominal  viscera  are 
not  sensitive  to  heat  and  cold,  Hertz,  Cook,  and  Schlesinger,  have 
reported  that  if  care  is  taken  to  introduce  hot  or  cold  water  into 
the  stomach  through  the  inner  of  two  tubes,  no  temperature 
sensation  is  experienced.  The  temperature  sensations  usually 
ascribed  to  the  stomach  they  attribute  to  stimulation  of  the 
oesophagus ;  for  if  the  water  is  introduced  when  the  tubes  are 
withdrawn  until  slightly  above  the  cardia,  the  subject  can  tell 
whether  it  is  hot  or  cold.  Hydrochloric  acid,  even  0-5  per 
cent.,  poured  into  a  normal  empty  stomach  produces  no  sensa- 
tion whatever,  but  strong  alcohol  (48  per  cent.)  injected  through 
a  gastric  fistula  causes  a  burning  sensation.  Conceivably,  how- 
ever, the  alcohol  is  in  part  regurgitated  into  the  oesophagus.13 

The  distressing  effect  of  a  foreign  object  in  the  stomach, 
such  as  a  thermometer-tube  or  a  balloon,  has  been  recorded  by 
Beaumont  and  by  Moritz  (see  p.  52).  The  two  conditions 
most  commonly  associated  with  gastric  pain  are  liberation  and 
cramp.  Observations  on  patients  with  gastric  ulcer  have  shown 
that  even  weak  acid  introduced  into  the  stomach  causes  pain.14 
The  pain  from  ulcer  in  the  stomach  or  intestine  is  explained  by 
Lennander  as  a  result  of  inflammation  of  the  lymphatic  vessels 


THE   EXTRINSIC   INNERVATION  203 

and  glands  which  drain  the  affected  region.  The  painful  cramp 
is  attributed  to  a  strong  contraction  of  a  part  of  the  alimentary 
canal  which  stretches  the  parietal  serosa  either  directly  or  through 
mesenteric  connections.  In  man  the  duodenum  and  the  colon, 
because  of  their  relations  to  the  abdominal  wall,  are  especially 
capable  of  causing  pain,  both  by  inflammations  and  by  powerful 
contractions.15 

The  clinical  evidence  of  the  insensitivity  of  the  viscera  has 
been  criticized  by  Kast  and  Meltzer.  Experimental  observations 
on  dogs  and  cats  indicated  to  them  that  the  operation  of  opening 
the  abdominal  cavity  may  have  an  inhibitory  effect  on  sensory 
impulses,  especially  in  states  of  bodily  weakness.  Unmistakable 
signs  of  pain  can  be  evoked,  they  declare,  if  after  a  small 
opening  is  made  in  the  body  wall  a  short  loop  of  intestine  is 
withdrawn  and  immediately  investigated.  In  their  experience, 
inflammation  increases  the  irritability.16  According  to  Duc- 
ceschi,  stimulation  of  the  gastric  wall  with  thermal,  mechanical, 
or  chemical  agencies  causes  characteristic  changes  in  the  rhythm 
and  frequency  of  respiration,  like  those  attending  stimulation  of 
sensory  nerves.  These  effects  are  produced  by  way  of  either 
the  vagus  or  splanchnic  paths.  The  afferent  fibres  of  the  vagi, 
like  the  efferent,  are  distributed  from  each  nerve  trunk  at  the 
cardia  to  only  one  side  of  the  stomach,  whereas  the  fibres  in  one 
cervical  vagus  are  sent  to  all  parts  of  the  organ.  Likewise  the 
afferent  fibres  in  each  splanchnic  nerve  are  connected  through 
filaments  from  the  coeliac  plexus  with  the  entire  surface  of  the 
stomach.  Thus  only  one  cervical  vagus  or  one  splanchnic  nerve 
would  be  necessary  to  carry  afferent  impulses  from  any  part  of 
the  gastric  wall  to  the  central  nervous  system.17  These  observa- 
tions on  the  sensitivity  of  the  gastro-intestinal  canal,  quite  apart 
from  irritation  of  the  abdominal  wall,  have  been  corroborated 
by  Ritter,18  whose  results  correspond  to  those  obtained  by  Kast 
and  Meltzer.  More  recently  Miller  has  shown  that  irritation  of 
the  gastric  mucosa  with  mustard  evokes  salivation,  rapid  respira- 
tion, and  the  vomiting  reflex.  All  these  effects  are  absent  if  the 
vagi  have  been  previously  cut.  He  was  unable  to  demonstrate 
that  the  splanchnics  transmit  sensory  impulses  of  any  kind  from 
the  gastric  mucosa.19 

From  the  above  brief  review  it  is  clear  that  important  unex- 
plained discrepancies  exist  among  investigators,  so  that  a 
definite  decision  as  to  the  immediate  origin  of  pain  sensations  in 


204          THE    MECHANICAL   FACTOKS    OF  DIGESTION 

the  walls  of  the  stomach  and  intestines  cannot  as  yet  be  made. 
There  is  no  doubt  that  disturbances  in  these  structures  result  in 
sensations  of  one  sort  or  another.  Aches,  pains,  vague  feelings 
of  heaviness,  are  all  experienced  in  pathological  conditions  of  the 
tract  below  the  diaphragm.  The  question  is  as  to  the  possibility 
of  these  conditions  affecting  the  central  nervous  system  immedi- 
ately and  not  by  way  of  spinal  nerves.* 

The  Extrinsic  Innervation  of  the  Small  Intestine. — Most  ob- 
servers have  attributed  to  the  vagus  nerves  motor  effects  on  the 
small  intestine.  After  section  of  the  splanchnic  nerves  and  in- 
terruption of  inhibitory  impulses  to  the  heart,  Bayliss  and 
Starling  found  that  repeated  stimulation  of  the  vagus  in  the 
neck  gave  consistent  results.  A  very  brief  inhibitory  phase  was 
followed  by  a  rise  of  tonus  and  a  gradual  increase  of  the  rhythmic 
contractions  to  an  extent  above  the  normal,  and,  as  soon  as  the 
stimulation  was  stopped,  by  an  immediate  and  considerable 
increase  of  tonus  and  augmentation  of  the  beat.  The  return  to 
the  original  state  is  slow  and  gradual.  The  vagus  nerves  appear, 
therefore,  to  convey  both  motor  and  inhibitory  fibres  to  the 
small  intestine,  although  the  inhibitory  effect  is  conceivably  due 
to  the  direct  nervous  stimulation  of  a  region  above  the  recording 
ring.20 

The  splanchnic  nerves  were  shown  by  Pfliiger  many  years  ago 
to  have  an  inhibitory  influence  on  the  movements  of  the  intes- 
tine.21 Although  other  investigators  have  since  described  motor 
effects  from  stimulation  of  sympathetic  fibres,  and  still  others 
have  believed  that  the  effects  are  opposite  on  the  longitudinal 

*  Among  the  sensations  referred  rather  indefinitely  to  the  abdomen  is  that 
of  hunger.  Either  directly  or  through  an  effect  on  the  parietal  peritoneum 
gastric  conditions  may  give  rise  to  this  sensation.  In  studying  auscultation  of 
the  abdominal  sounds  I  had  occasion  to  note  repeatedly  that  the  sensation  of 
hunger  was  not  continuous,  but  recurrent,  and  that  its  disappearance  was 
commonly  associated  with  a  rather  loud  gurgling  sound  as  heard  through  the 
stethoscope.  Since  then  I  have  paid  occasional  attention  to  the  matter,  and 
have  experienced  disappearance  of  the  sensation  as  gas  was  gurgling  upward 
through  the  cardia.  That  the  gas  was  rising  rather  than  being  forced  down- 
ward was  shown  by  its  regurgitation  immediately  after  the  sound  was  heard. 
As  a  suggestion  I  venture  to  state  that  hunger  is  due  to  contraction  of  the 
nearly  empty  stomach.  The  contracted  stomach  in  fasting  animals  has  been  noted 
(His,  Arch.  f.  Anat.,  1903,  p.  345).  In  the  cat,  after  forty-eight  hours  of 
fasting,  the  organ  may  be  so  small  as  to  look  like  a  slightly  enlarged  duodenum 
(Wolff,  Dissertation,  Giessen,  1902,  p.  9).  Of  course,  the  hungry  stomach,  thus 
contracted,  is  ready  at  once  to  begin  rhythmic  pulsations  on  being  stretched 
by  food.  In  this  connection  it  is  of  interest  to  note  that  the  disagreeable 
sensation  of  hunger,  in  my  experience,  is  momentarily  abolished  a  few  seconds 
after  swallowing,  a  result  which  can  be  explained  as  due  to  the  inhibitioa  of 
gastric  contraction  by  vagus  influences,  in  the  manner  above  described. 


THE   EXTRINSIC    INNERVATION  205 

and  circular  muscle,  the  careful  work  of  Bayliss  and  Starling 
has  demonstrated  only  inhibition  of  activity  in  each  muscular 
layer. 

Since  the  splanchnic  nerves  bear  vasoconstrictor  impulses  to 
the  bloodvessels  of  the  intestines,  and  since  the  primary  result 
of  anaemia  is  cessation  of  intestinal  activity,  the  inhibitory  effect 
these  nerves  produce  might  be  due  to  a  diminished  blood-supply. 
This  interpretation  of  the  results  of  sympathetic  impulses  Bayliss 
and  Starling  were  able  to  exclude  by  causing  the  usual  effects 
immediately  after  the  death  of  the  animal,  when  the  circulation 
was  no  longer  present.22 

The  normal  functions  of  the  two  sets  of  nerves  seem  to  be 
exercised  continuously.  After  complete  severance  of  the  splanch- 
nic nerves,  for  example,  I  found  that  the  rate  of  passage  of  lean 
beef  through  the  small  intestine  was  much  accelerated,  whereas 
after  total  vagus  section  the  passage  was  slower  than  normal.23 
Probably  the  vagus  nerves  act  on  the  intestine,  just  as  they  act 
on  the  stomach,  to  produce  a  tonic  condition  of  the  neuromuscu- 
lature.  Magnus  has  reported  that  it  is  advisable,  in  studying 
isolated  pieces  of  the  intestine,  to  take  them  from  a  normally 
fed  animal,  since  the  intestine  of  a  fasting  animal  is  less  active. 
If,  however,  the  animal  has  been  without  food  for  three  days, 
the  intestine  begins  activity  as  soon  as  placed  in  Ringer's  solu- 
tion. The  condition  in  the  last  instance  seems  not  unrelated  to 
the  readiness  for  activity  in  the  highly  tonic  fasting  stomach. 

The  Extrinsic  Innervation  of  the  Large  Intestine. — Whether 
vagus  fibres  reach  the  large  intestine  is  still  in  doubt.  Bayliss 
and  Starling  were  unable  to  demonstrate  that  vagus  stimulation 
affected  any  part  of  the  large  intestine.24  On  the  other  hand, 
Meltzer  and  Auer  observed  that  vagus  stimulation  caused  strong 
contraction  of  the  caecum  in  the  rabbit.25  Apart  from  this 
possible  vagus  innervation,  the  large  intestine  receives,  as  already 
stated,  a  motor  supply  through  the  sacral  visceral  nerves,  and 
an  inhibitory  supply  from  the  lumbar  cord  through  the  sympa- 
thetic system  by  way  of  the  inferior  mesenteric  ganglion.  The 
sacral  nerves  (from  sacral  roots  ii.  and  iii.,  and  occasionally  i.,  in 
the  cat)  do  not  pass  directly  from  the  spinal  cord  to  the  colon, 
but  end  in  ganglia  at  the  side  of  the  rectum  and  the  neck  of  the 
bladder.  After  nicotine  has  abolished  conduction  through  these 
ganglia,  stimulation  of  the  post-ganglionic  fibres  still  causes 
contraction.  There  exist,  consequently,  in  relation  to  the  colon. 


206         THE   MECHANICAL  FACTORS   OF  DIGESTION 

peripheral  neurons  of  the  motor  path  which  are  quite  distinct 
from  the  my  enteric  plexus.26 

Although  results  have  been  reported  indicating  a  "  crossed 
innervation  "  of  the  two  muscular  coats — i.e.,  contraction  or 
inhibition  of  the  circular  coat  by  impulses  that  simultaneously 
inhibit  or  contract  the  longitudinal  coat27 — Bayliss  and  Starling 
in  their  careful  observations  found  that  sympathetic  stimulation 
caused  pure  inhibition,  while  sacral  stimulation  after  a  momen- 
tary inhibition  called  forth  contraction  of  both  the  circular  and 
longitudinal  coats.28  These  observations  Elliott  and  Barclay- 
Smith  have  confirmed,  but  they  found  that  the  pelvic  nerves  are 
distributed  only  to  that  part  of  the  colon  which  is  involved  in 
the  act  of  defaecation.  For  example,  these  nerves  supply  all  but 
the  caecum  in  the  dog,  and  the  distal  two-thirds  of  the  colon  in 
the  cat.  The  region  where  antiperistalsis  prevails  does  not, 
therefore,  receive  motor  impulses.  Stimulation  of  the  pelvic 
nerves  first  increases  the  tonus  of  the  mid-region,  whence  then 
antiperistaltic  waves  may  arise ;  but  continued  stimulation 
causes  the  distal  half  of  the  colon  to  shorten,  and  thereafter  a 
strong  contraction  of  the  circular  coat  to  spread  downward  in 
the  manner  already  described  for  natural  evacuation.29 

The  normal  functioning  of  the  two  sets  of  nerves  is  indicated 
by  the  results  of  sectioning,  as  well  as  by  the  results  of  stimulating 
them.  Severance  of  the  sympathetic  fibres  supplying  the  large 
intestine  causes  in  the  cat  and  the  rabbit  no  lasting  disturbance 
of  the  motor  functions.  After  removal  of  the  motor  impulses, 
however,  by  destruction  of  the  spinal  cord  or  by  cutting  the 
nerves,  the  functions  of  the  colon  in  the  rat  and  the  rabbit  are 
evidently  disturbed.  Faeces  accumulate,  and  the  contractions 
of  the  gut  are  sluggish  and  weak.30  Langley  and  Anderson's 
observations  on  the  cat  with  sacral  nerves  cut  indicate  a  similar 
defect  of  function.31  These  functional  defects  are  not  the  tem- 
porary result  of  motor  nerve  section,  like  the  inactivity  of  the 
stomach  after  severance  of  the  vagi,  for  they  were  observed  in 
the  rat  and  rabbit  six  weeks  after  operation.  They  may  be  due 
in  part,  however,  to  the  continuance  of  inhibitory  sympathetic 
impulses  acting  in  the  absence  of  their  usual  opponents.  This 
suggestion  is  supported  by  the  observation  of  Goltz  and  Ewald, 
that,  although  removal  of  both  sets  of  nerves  by  destruction  of 
the  lumbar  and  sacral  cord  results  in  a  diarrhoea  lasting  several 
days,  yet  recovery  occurs,  and  after  a  few  weeks  the  dog  exhibits 


THE   EXTRINSIC   INNERVATION  207 

normal  activity  of  the  colon,  with  faeces  of  usual  consistency 
discharged  at  customary  intervals.  After  defaecation  the  rectum 
is  found  empty.32 

As  already  stated,  defsecation  is  a  reflex  initiated  by  the 
presence  of  faeces  in  the  rectum.  The  section  of  sensory  roots 
of  the  sacral  nerves  supplying  the  rectal  mucosa  causes  an  aboli- 
tion of  the  normal  co-ordination.33 

The  Innervation  of  the  Sphincters. — Although  the  cardiac  and 
pyloric  sphincters  are  affected  by  local  conditions,  they  are,  like 
the  rest  of  the  canal,  subject  also  to  the  central  nervous  system. 
The  extrinsic  innervation  of  the  cardia  has  been  considered.  At 
the  pylorus  the  usual  result  of  vagus  stimulation  is  contraction,34 
but  Langley  observed  also  at  times  dilatation.35  According  to 
Openchowski,  the  same  stimulation  of  the  vagus  that  produces 
relaxation  of  the  cardia  simultaneously  produces  closure  of  the 
pylorus,  a  co-ordination  that  is  evidently  serviceable  in  vomiting. 
The  splanchnics  cause  in  the  rabbit  contraction  of  the  pyloric 
sphincter,  and  when  adrenalin  is  given  the  same  result  is  to  be 
seen.36  In  dogs,  splanchnic  stimulation  is  said  to  relax  or  open 
a  closed  pylorus.37 

The  ileo-colic  sphincter  was  unaffected,  in  Elliott's  experience, 
by  vagus  stimulation.  Its  tonic  closure  is  due  to  impulses  from 
the  central  nervous  system  by  way  of  the  splanchnics.  If  these 
nerves  are  stimulated,  the  tonus  of  the  sphincter  increases ;  if 
they  are  cut  or  the  spinal  cord  destroyed,  the  sphincter  becomes 
toneless  and  permits  material  to  pass  back  from  the  colon.38 

Both  the  internal  and  external  anal  sphincters  are  normally 
in  a  state  of  tonic  contraction.  Although  the  external  sphincter 
is  composed  of  striated  muscle,  its  connection  with  extrinsic 
nerves  is  not  interrupted  by  curare.  Destruction  of  the  spinal 
cord,39  or  removal  of  the  ganglia  between  the  cord  and  the 
viscera,40  causes  a  loss  of  tonus  of  the  sphincters,  from  which, 
however,  they  soon  recover.  Stimulation  of  the  sympathetic 
nerves  in  the  cat  causes  contraction  of  the  internal  sphincter, 
and  in  the  rabbit  and  dog  at  times  contraction,  and  at  other  times 
relaxation.41  The  sacral  nerves,  when  artificially  excited,  cause 
closure  of  this  sphincter  in  the  dog,  relaxation  in  the  rabbit,  and 
both  effects  in  the  cat. 

The  diverse  results  reported  as  the  result  of  stimulating  the 
sphincters  are  perhaps  due  to  the  artificial  character  of  the 
excitation.  In  physiological  conditions  they  co-operate  with 


208          THE   MECHANICAL   FACTORS    OF  DIGESTION 

other  processes ;  the  orderliness  of  their  action  then  is  probably 
produced  through  nervous  connections.  In  the  case  of  the  cardia, 
Kronecker  and  Meltzer  showed  the  manner  in  which  the  physio- 
logical relaxation  is  associated  with  the  passage  of  a  bolus  into 
the  stomach.  Further  observations  on  the  sphincters  with  refer- 
ence to  physiological  stimuli  will  be  necessary  before  the  func- 
tions of  the  extrinsic  nerves  can  be  clearly  denned.  Meanwhile 
the  only  generalization  which  has  been  offered  is  that  of  Elliott, 
who  has  stated  that  "  If  the  quiet  lodgment  of  the  contents  be 
facilitated  by  the  presence  of  sympathetic  inhibitor  nerves  to  the 
body  of  the  viscus,  there  will  also  be  sympathetic  motor  nerves 
to  the  sphincter  closing  the  exit."42  Thus  adrenalin,  which 
stimulates  as  sympathetic  impulses  stimulate,  causes  relaxation 
of  the  entire  gastro-intestinal  tract,  except  at  the  pyloric,  ileo- 
colic,  and  internal  anal  sphincters. 


REFERENCES. 

1  Langley,  Ergeb.  d,  Physiol.,  1903,  ii.2,  p.  832. 

2  Ducceschi,  Arch,  di  Fisiol.,  1905,  ii.,  p.  52. 

3  Bayliss  and  Starling,  J.  Physiol. ,  1899,  xxiv.,  p.  143. 

4  Langley,  loc.  cit.,  p.  853. 

5  May,  J.  Physiol.,  1904,  xxxi.,  pp.  262,  264. 

6  Cannon,  Am.  J.  Physiol.,  1906,  xvii.,  p.  431. 

7  Cannon,  Am.  J.  Physiol.,  1906,  xvii.,  p.  432. 

8  Pawlow,  The  Work  of  the  Digestive  Glands,  London,  1902,  p.  50. 

9  Cannon  and  Lieb,  Am.  J.  Physiol.,  1911,  xxvii.,  p.  xiii. 

10  Elliott,  /.  Physiol.,  1905,  xxxii.,  p.  420. 

11  Cannon,  Am.  J.  Physiol.,  1906,  xvii.,  p.  441. 

12  Lennander,  Arch.  f.  Verdauungskr.,  1907,  xiii.,  p.  467. 

13  Hertz,  Cook,  and  Schlesinger,  J.  Physiol.,  1908,  xxxvii.,  p.  481. 

14  Bonninger,  Berl.  klin.  Wchnschr.,  1908,  xlv.,  p.  396. 

15  See  Lennander,  loc.  cit.,  also  J.  Am.  Med.  Ass.,  1907,  xlix.,  p.  836 ;    Wilms, 
Mitth.  a.  d.  Grenzgeb.  d.  M.  u.  Chir.,  1906,  xvi.,  p.  609. 

16  Kast  and  Meltzer,  Mitth.  a.  d.  Grenzgeb.  d.  M.  u.  Chir.,  1909,  xix.,  p.  616. 

17  Ducceschi,  Arch,  di  Fisiol.,  1905,  ii.,  p.  525. 

18  Ritter,  Zentralbl.  f.  Chir.,  1908,  xxxv.,  p.  611. 

19  Miller,  J.  Physiol.,  1910,  xli.,  p.  410. 

20  See  Starling,  Ergeb.  d.  Physiol.,  1902,  i.2,  p.  460. 

21  Pfiiiger,  U.  d.  Hemmungsnervensystem  f.  d.  peristalt.  Beweg.  d.  Gedarme, 
Berlin,  1857. 

22  Bayliss  and  Starling,  loc.  cit.,  p.  124. 

23  Cannon,  Am.  J.  Physiol.,  1906,  xvii.,  p.  438. 

24  Bayliss  and  Starling,  J.  Physiol.,  1900,  xxvi.,  p.  114. 

25  Meltzer  and   Auer,  Proc.  Soc.  Exper.  Biol.    H.,   New  York,    1907,   iv., 
p.  39. 

26  Langley  and  Anderson,  J.  Physiol.,  1895,  xviii.,  p.  67,  xix.,  pp.  71,  372  ; 
1896,  xx.,  p.  372. 

27  Ehrmann,  Wien.  med.  Jahrb.,  1885,  p.  115  ;  Fellner,  Arch.  f.  d.  ges.  Physiol., 
1894,  Ivi.,  p.  542  ;  Courtade  and  Guyon,  Arch,  de  Physiol.,  1897,  xxix.,  p.  881. 

J8  Bayliss  and  Starling,  J.  Physiol.,  1900,  xxvi.,  p.  107. 

29  Elliott  and  Barclay-Smith,  J.  Physiol.,  1904,  xxxi.,  pp.  282,  283. 

30  Elliott  and  Barclay-Smith,  loc.  cit.,  p.  288. 


THE   EXTRINSIC   INNERVATION  203 

31  Langloy  and  Anderson,  J.  Physiol.,  1896,  xix.,  p.  380. 

52  Goltz  and  Ewald,  Arch.  f.  d.  ges.  Physiol.,  1896,  Ixiii.,  p.  331. 

13  Merzbaoher,  ^rcfe.  /.  d.  ges.  Physiol.,  1902,  xcii.,  p.  597. 

34  See  Openchovvski,  loc.  tit.,  p.  4. 

35  Langley,  «/.  Physiol.,  1898,  xxiii.,  p.  414. 

36  Elliott,  J.  Physiol.,  1905,  xxxii.,  p.  420. 

3r  Oser,  Ztschr.  /.  Idin.  Med.,  1892,  xx.,  p.  291. 

38  Elliott,  J.  Physiol.,  1904,  xxxi.,  p.  166. 

39  Goltz  and  Ewald,  loc.  tit.,  p.  399. 

40  Frankl-Hochwart  and   Frohlich,  Arch.  f.  d.  ges.  PhytioL,   1900,  Ixxxi., 
p.  474. 

41  Langley  and  Anderson,  J.  Physiol.,  1895,  xviii.,  p.  104  ;  Frankl-Hochwart 
and  Frohlich,  loc.  tit.,  p.  462. 

42  Elliott,  J.  Physiol.,  1905,  xxxii.,  p.  422. 


14 


CHAPTER  XVI 

DEPRESSIVE  NERVOUS  INFLUENCES  AFFECTING  GASTRO- 
INTESTINAL MOVEMENTS 

THUS  far  our  review  of  the  extrinsic  innervation  of  the  alimentary 
canal  has  shown  that  two  influences  are  affecting  its  movements 
— depressive  influences  through  the  sympathetic,  and  augmentor 
influences  through  the  bulbar  and  sacral  nerves.  It  is  clear  that 
absence  of  activity  may  be  due  either  to  a  failure  of  the  impulses 
which  establish  the  necessary  tonic  state  of  the  musculature,  or 
to  the  predominance  of  the  impulses  which  depress.  In  these 
relations  the  phenomena  attending  a  condition  of  general  bodily 
weakness  are  of  interest. 

The  Influence  of  General  Asthenia. — When  the  nervous  con- 
nections between  the  alimentary  canal  and  the  central  nervous 
system  are  intact,  nothing  is  more  remarkable  than  the  respon- 
siveness of  the  canal  to  general  asthenia.  I  have  had  repeated 
opportunity  to  examine  the  movements  of  the  stomach  and 
intestines  in  animals  suffering  from  "  distemper,"  with  purulent 
inflammation  of  the  nose  and  eyes,  with  soft  toneless  muscles, 
and  every  appearance  of  debility.  Under  these  circumstances, 
food  will  lie  in  the  stomach  or  intestine  all  day  without  the 
slightest  sign  of  a  peristaltic  wave  affecting  it.  There  is  total 
stoppage  of  the  motor  activity  of  the  digestive  organs. 

The  result  is  quite  different  when  the  canal  is  disconnected 
from  the  spinal  cord  and  brain.  In  such  a  state  the  stomach 
and  small  intestine  have  been  observed  exhibiting  their  normal 
activities,  although  the  animal  was  to  the  last  extremity  feeble 
and  toneless.1 

The  absence  of  activity  in  states  of  bodily  depression  is  prob- 
ably due  in  greatest  measure  to  the  lack  of  necessary  tonus  in 
the  gastro-intestinal  musculature.  The  animals  manifest  no  signs 

210 


DEPRESSIVE    NERVOUS    INFLUENCES  211 

of  appetite,  and  do  not  eat  spontaneously.  There  is,  conse- 
quently, no  occasion  for  the  establishment  of  the  "  psychic 
tonus  "  which  I  have  suggested  as  a  resultant  of  the  eager 
taking  of  food.  It  is  possible,  however,  that  when  all  nerves 
are  intact  inhibitory  influences  through  the  splanchnics  may  also 
play  a  part  in  maintaining  the  quiet  state,  for  fairly  normal 
activities  have  been  observed  in  two  cases  of  asthenia  when  only 
splanchnic  nerves  had  been  severed  and  the  vagi  were  still 
intacfc. 

Post-operative  Paralysis. — One  of  the  most  distressing  instances 
of  inactivity  of  the  bowel  is  that  seen  occasionally  after  surgical 
operations  on  the  abdomen.  From  what  we  have  learned  of 
the  controlling  factors,  we  should  expect  that  this  inactivity 
might  be  due  either  to  general  causes  working  through  the 
central  nervous  system,  or  to  local  factors,  such  as  the  inefficiency 
of  the  myenteric  plexus  or  the  muscles  subject  to  it.  With  the 
hope  of  determining  the  relative  importance  of  the  modifiable 
procedures  in  surgical  operations,  F.  T.  Murphy  and  I  under- 
took to  learn  the  effects  of  etherization,  and  of  exposing, 
cooling,  and  handling  the  alimentary  canal,  on  the  passage  of 
food  from  the  stomach  and  through  the  small  intestine.2 

The  effect  of  etherization  was  tested  by  etherizing  one  half- 
hour  or  one  hour  and  a  half,  and  feeding  about  a  half-hour  there 
after  25  c.c.  of  the  standard  potato  and  bismuth  subnitrate 
mixture.  By  the  method  already  described  the  aggregate  length 
of  the  food-masses  in  the  intestine  was  determined  at  regular 
intervals  after  feeding.  The  results  are  shown  in  Fig.  34. 
Clearly,  anaesthesia  alone,  compared,  for  example,  with  high 
intestinal  operation  accompanied  by  anaesthesia  (see  p.  126), 
has  relatively  slight  effect.  The  initial  passage  of  food  from 
the  stomach  was  delayed  and  the  outgo  was  slow.  The  passage 
through  the  small  intestine  was  also  slow.  Material  reached  the 
colon,  not  after  two  or  three  hours,  as  in  normal  conditions,  but 
only  after  four,  five,  and  six  hours.  But  etherization,  neverthe- 
less, did  not  cause  inactivity  of  the  canal. 

The  effect  of  exposure  was  tested  by  displaying  the  stomach 
and  small  intestine  as  much  as  possible  without  manipulation, 
during  a  half-hour's  anaesthesia.  The  visible  serosa  became  dry 
and  lustreless.  At  the  end  of  the  half-hour  the  abdomen  was 
closed,  and  when  the  animal  had  recovered  from  the  ether  the 
standard  food  was  fed.  Fig.  35  represents  graphically  the 


212 


THE   MECHANICAL   FACTORS    OF   DIGESTION 


differences  between  the  normal  condition  and  that  following 
exposure.  As  long  ago  as  1872  v.  Braam  Houckgeest3  noted 
the  disturbing  effect  of  exposure  on  the  action  of  the  intestines, 


40 
3C 
20 
10 

Houi 

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FIG.  34. 

The  continuous  line  represents  the  normal  condition  ;  the  dash-line  the  typical 
condition  after  etherization  for  a  half -hour ;  and  the  dot-line  the  typical 
condition  after  etherization  for  an  hour  and  a  half. 

and  to  avoid  it  he  devised  the  warm  saline  bath  as  the  medium 
in  which  to  retain  the  normal  conditions  when  the  abdomen  is 
opened.  The  inhibitory  effect  of  exposure  might  be  expected  to 
exert  a  disturbing  after-effect.  That  seems  not  to  be  the  case. 

cm. 


40 
3C 
2( 
10 

Hou] 

I 

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FIG.  35. 

The  continuous  line  represents  the  normal  condition  ;  the  dash-line  the  typical 
condition  following  etherization,  with  exposure  of  the  stomach  and 
intestines  to  the  air  for  a  half -hour. 

The  passage  of  the  food  through  the  canal  was  hardly  different 
from  that  which  followed  etherization  alone. 
Cooling  the  body  causes  a  cessation  of  the  movements  of  the 


DEPRESSIVE   NERVOUS    INFLUENCES 


213 


alimentary  canal.4  It  was  possible  that  a  temporary  cooling  of 
the  stomach  and  intestines,  without  drying,  would  stop  °the 
movements  of  these  organs.  To  test  this  possibility,  sterile 
normal  salt  solution  at  20°  C.  was  poured  repeatedly'  into  the 
opened  abdominal  cavity  for  ten  minutes  during  the  usual  half- 
hour  of  etherization.  The  procedure  reduced  the  body  tem- 
perature to  nearly  33°  C.  About  forty  minutes  after  the  abdo- 
men had  been  closed  and  the  etherization  discontinued,  the  animal 
was  given  the  standard  food.  Fig.  36  represents  graphically  the 
results.  The  discharge  from  the  stomach  again  started  some- 
what slowly,  but  the  passage  through  the  small  intestine  was 
surprisingly  rapid.  The  sharp  drop  in  the  curve  between  the 


cm. 


40 
30 
20 
10 

Hou 

/ 

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\: 

/ 

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--- 

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re  i     1           2           3           4           5           b          7 
FIG.  36. 

The  continuous  line  represents  the  normal  condition  ;  the  dash-line  the  typical 
condition  after  etherization  and  cooling  of  the  abdominal  cavity  with 
sterile  normal  salt  solution  at  20°  C.  The  early  drop  in  the  dash-line  is 
due  to  the  rapid  passage  of  the  food  into  the  large  intestine. 

second  and  third  hours  is  thus  explained.  Although  the  degree 
of  cooling  was  excessive,  the  departure  of  food  from  the  stomach 
was  about  as  rapid  as  when  etherization  alone  disturbed  the 
normal  state.  And  the  rapid  passage  of  the  food  through  the 
small  intestine  certainly  lends  no  support  to  the  idea  that  cooling 
causes  enteric  paresis. 

Handling  the  stomach  and  intestines  may  have  different  effects 
according  to  different  degrees  of  manipulation,  and  these  degrees 
are  difficult  to  express.  In  the  most  severe  treatment  the  organs 
were  stripped  between  the  thumb  and  first  finger  with  consider- 
able pressure,  as  would  be  done  in  forcing  out  the  contents ;  in 
the  less  severe  treatment  the  organs  were  fingered  gently  in  air, 
or  in  a  trickling  stream  of  warm  normal  salt  solution,  with  the 


214 


THE   MECHANICAL    FACTORS    OF   DIGESTION 


parts  protected  from  the  fingers  by  absorbent  cotton  wet  with 
the  solution,  or  run  through  the  bare  fingers  within  the  peritoneal 
cavity.  About  an  hour  after  stopping  the  anaesthetic  the  animals 
were  fed  as  in  former  experiments,  and  the  observations  were 
taken  at  the  usua]  intervals.  The  relation  of  typical  cases  to  the 
normal  condition  is  shown  graphically  in  Fig.  37.  In  examining 
these  curves,  we  should  remember  that  since  neither  etherization 
alone,  nor  such  cooling  and  drying  as  the  viscera  in  some  cases 
suffered,  cause  a  delay  in  the  passage  of  food  from  the  stomach, 
the  delay  must  have  been  due  to  the  manipulation.  Even  when 
the  stomach  and  intestines  were  handled  most  gently,  either 


cm 


40 


\ 


Houra 


FIG.  37. 


The  heavy,  continuous  line  represents  the  normal  condition  ;  the  light,  con- 
tinuous line  the  typical  condition  after  har  dling  the  stomach  and  intestine 
gently  under  warm  normal  salt  solution  ;  the  dash-line  the  typical  con- 
dition after  handling  the  organs  gently  in  the  peritoneal  cavity  ;  the  dash- 
and-dot  line  after  handling  them  gently  in  the  air  ;  and  the  dot-line  after 
handling  them  severely  in  the  air. 

under  warm  normal  salt  solution  or  within  the  peritoneal  cavity, 
no  movements  of  the  stomach  were  seen,  and  no  discharge  into 
the  intestine,  for  three  full  hours  after  the  feeding.  Even  after 
the  first  departure  of  food  from  the  stomach  the  discharge  con- 
tinued very  slowly,  as  shown  by  the  sloping  of  the  curve.  The 
passage  through  the  small  intestine  was  also  retarded.  In  only 
one  case  did  food  appear  in  the  large  intestine  before  the  end  of 
the  seven  hours  of  observation. 

When  the  organs  were  removed  from  the  abdomen  and  handled 
gently  in  air,  the  movement  of  the  food  was  retarded  to  a  greater 
degree  than  when  they  were  fingered  in  the  peritoneal  cavity  or 
under  warm  normal  salt  solution.  So  great  was  the  retardation 


DEPRESSIVE   NERVOUS   INFLUENCES  215 

in  one  case  that  not  all  the  food  had  passed  into  the  large 
intestine  from  the  ileum  twenty-six  hours  after  the  feeding. 
Indeed,  the  condition  then  was  that  reached  normally  in  about 
five  hours. 

With  rougher  treatment  in  air  food  was  first  passed  from  the 
stomach  only  after  four  hours.  Thenceforward  it  departed  very 
slowly,  and,  as  shown  by  the  permanence  of  position  from 
observation  to  observation,  was  carried  through  the  small 
intestine  with  extreme  sluggishness.  In  one  case  of  severe 
manipulation  no  food  had  left  the  stomach  at  the  end  of  seven 
hours,  and  in  another  case  the  food  had  not  yet  reached  the 
large  intestine  twenty-four  hours  after  the  feeding  (the  food 
used  begins  to  appear  there  normally  at  the  end  of  two  or  three 
hours).  Only  a  slight  amount  of  food  was  in  the  small  intestine, 
and  the  stomach  was  still  well  filled.  Manipulation  of  the 
stomach  and  intestine,  therefore,  even  gently  and  under  most 
favourable  circumstances,  produced  in  our  experiments  much 
greater  effect  in  the  direction  of  post- operative  inactivity 
than  any  other  of  the  factors  concerned  in  the  manner  of 
operating. 

Whether  manipulation  acted  locally  on  the  neuromusculature 
of  the  alimentary  canal  or  indirectly  through  reflex  inhibitions 
from  the  central  nervous  system  remained  to  be  determined. 
The  observation  of  Bayliss  and  Starling  that  manipulation  of 
the  intestine  at  one  point  inhibits  activities  at  other  points6 
was  suggestive  of  reflex  inhibition. 

In  order  to  test  the  source  of  the  post-operative  inactivity, 
Murphy  and  I  undertook  a  further  series  of  experiments.6 
Evidently,  if  the  inactivity  is  due  to  reflex  inhibition,  handling 
after  the  splanchnic  nerves  are  cut  ought  to  have  no  effect, 
since  the  pathway  for  inhibitory  impulses  is  destroyed.  If 
after  severance  of  the  splanchnics,  however,  manipulation  still 
produces  inactivity,  th.e  result  can  be  attributed  to  local  dis- 
turbance. 

Animals  in  which  the  splanchnic  nerves  had  been  severed 
aseptically  several  days  before  were  treated  in  the  same  manner 
as  the  normal  animals  on  which  the  earlier  observations  were 
made.  During  the  half-hour  of  etherization  the  abdomen  was 
opened,  and  the  stomach  and  intestines,  under  aseptic  precau- 
tions, were  stripped  between  the  fingers — i.e.,  roughly  handled. 
Within  an  hour  after  etherization  ceased  the  animals  were  given 


216          THE   MECHANICAL   FACTOKS    OF   DIGESTION 

the  standard  food,  and  observed  at  the  regular  intervals  after 
the  feeding. 

In  one  animal  there  was  no  discharge  from  the  stomach  during 
seven  hours  of  observation,  though  the  next  day  the  stomach 
was  largely  empty.  Another  animal  vomited  the  gastric  con- 
tents after  the  first  hour.  In  a  third  case  nothing  left  the 
stomach  during  the  first  six  hours,  and  then  the  outgo  was  slow. 
In  still  another  instance  food  began  fco  pass  the  pylorus  at  the 
end  of  an  hour,  but  the  exit  was  very  slow,  and  at  the  end  of 
seven  hours  no  food  had  reached  the  large  intestine.  These 
results  correspond  closely  to  the  results  following  manipulation 
of  the  stomach  and  intestines  of  normal  animals.  In  both  there 
was  a  marked  retardation  of  the  discharge  of  food  from  the 
stomach,  and  a  sluggish  condition  of  the  small  intestine.  The 
effects  of  handling,  therefore,  are  not  necessarily  the  consequence 
of  reflex  inhibitions  from  the  spinal  cord,  but  can  be  explained 
as  disturbances  of  the  local  mechanisms  in  the  wall  of  the  gut. 
The  observation  of  Meltzer  and  Auer  that  destruction  of  the 
spinal  cord  in  the  rabbit  does  not  prevent  the  direct  inhibition 
of  peristalsis,  observed  when  the  abdomen  is  opened,7  and  our 
observation  of  local  inhibition,  are  in  perfect  agreement. 

Lasting  inactivity  of  the  gastro-intestinal  tract  can  also  be 
produced  reflexly.  Thus  Meltzer  and  Auer  found  that  dissec- 
tion of  the  skin  over  the  abdomen  produced  reflex  inhibition  of 
peristalsis,  and  Murphy  and  I  found  that  trauma  of  the  testicles 
during  the  half-hour  of  etherization  retarded  the  exit  from  the 
stomach  for  four  or  five  hours,  and  caused  the  exit  thereafter  to 
be  characteristically  slow.  The  movement  through  the  small 
intestine  was  likewise  very  sluggish  ;  in  only  one  case  out  of  ten 
did  the  potato  reach  the  colon  within  six  hours.  If  the  splanchnic 
nerves  have  been  previously  severed,  trauma  of  the  testicle  has 
no  effect  whatever ;  indeed,  the  results  observed  in  these  cases 
compare  favourably  with  those  from  animals  in  quite  natural 
conditions. 

The  animals  used  in  these  experiments  were  vigorous  and 
normal.  The  trauma  to  which  they  were  subjected  was  done 
under  anaesthesia  when  nervous  conduction  may  be  much 
depressed.  The  intestine  of  these  animals  also  may  be  less 
sensitive  to  manipulation  than  is  the  human  intestine.  It  is 
probable,  therefore,  that  if  the  experimental  conditions  were 
superposed  on  a  state  of  bodily  weakness,  or  were  performed 


DEPRESSIVE   NERVOUS    INFLUENCES  217 

without  anaesthesia,  or  were  long  continued,  as  in  states  of  in- 
flammation— thus  simulating  common  conditions  in  human 
beings — the  results  would  have  been  even  more  pronounced. 

From  the  foregoing  evidence  it  is  clear  that  in  any  case  of 
adynamic  ileus  a  distinction  must  be  made  between  the  inactivity 
due  to  local  disturbances  in  the  gastro-intestinal  wall  and  in- 
activity due  to  inhibitory  impulses  from  the  central  nervous 
system.  In  any  case  of  unnatural  quiescence  the  first  considera- 
tion is  to  determine  its  source.  If  the  inhibition  is  extrinsic, 
any  agent  that  will  stop  the  delivery  of  inhibitory  influences 
from  the  spinal  cord  will  permit  the  stomach  and  intestines  to 
resume  the  functions  of  which  they  are  independently  capable. 
If,  on  the  other  hand,  the  inactivity  is  the  immediate  effect  of 
local  disturbance,  this  same  agent  will  have  no  effect  in  pro- 
moting the  restoration  of  peristalsis.  Thus,  in  our  experiments 
we  found  that  physostigmine  salicylate  produced  a  marked,  but 
temporary,  increase  of  peristalsis  in  cases  of  reflex  inhibition  of 
the  alimentary  canal,  but  that  tincture  of  aloes,  which  is  particu- 
larly effective  in  promoting  peristalsis  in  the  cat,  was  quite  in- 
effective after  such  manipulation  of  the  gut  as  results  in  paralysis.8 
The  various  conditions  that  affect  the  alimentary  canal  locally 
or  reflexly  have  not  yet  been  experimentally  studied,  but  mani- 
festly on  such  a  study  depends  the  possibility  of  rational  judg- 
ment in  any  particular  case. 

The  Influence  of  Emotions. — In  my  earliest  observations  on  the 
stomach9  I  had  difficulty,  because  in  some  animals  peristalsis  was 
perfectly  evident,  and  in  others  there  was  no  sign  of  activity. 
Several  weeks  passed  before  I  discovered  that  this  difference  in 
response  to  the  presence  of  food  in  the  stomach  was  associated 
with  a  difference  of  sex.  The  male  cats  were  restive  and  excited 
on  being  fastened  to  the  holder,  and  under  these  circumstances 
gastric  peristalsis  was  absent ;  the  female  cats,  especially  if 
elderly,  submitted  with  calmness  to  the  restraint,  and  in  them 
peristaltic  waves  took  their  normal  course.  Once  a  female  with 
kittens  turned  from  her  state  of  quiet  contentment  to  one  of 
apparent  restless  anxiety.  The  movements  of  the  stomach  im- 
mediately stopped,  and  only  started  again  after  the  animal  had 
been  petted  and  had  begun  to  purr.  I  later  found  that  by 
covering  the  cat's  mouth  and  nose  with  the  fingers  until  a  slight 
distress  of  breathing  occurred  the  stomach  movements  could  be 
stopped  at  will.  Thus,  in  the  cat  any  sign  of  rage,  or  distress, 


218          THE   MECHANICAL   FACTORS    OF   DIGESTION 

or  mere  anxiety,  was  accompanied  by  a  total  cessation  of  the 
movements  of  the  stomach.  I  have  watched  with  the  X  rays 
the  stomach  of  a  male  cat  for  more  than  an  hour,  during  which 
time  there  was  not  the  slightest  beginning  of  peristaltic  activity, 
and  yet  the  only  visible  indication  of  excitement  in  the  animal 
was  a  continued  to-and-fro  twitching  of  the  tail. 

What  is  true  of  the  cat  has  been  proved  true  also  of  the  rabbit, 
dog,  and  guinea-pig.  Even  slight  psychic  disturbances  were 
accompanied  by  stoppage  of  peristalsis.10  My  observations  on 
the  rabbit  have  been  confirmed  by  Auer,11  who  found  that  the 
handling  of  the  animal  incident  to  fastening  it  gently  to  a  holder 
stopped  gastric  peristalsis  for  a  variable  length  of  time ;  and  if 
the  animal  was  startled  in  any  way,  or  struggled,  peristalsis  was 
again  abolished.  The  observations  on  the  dog  also  have  been 
confirmed.  Lommel12  found  that  small  dogs  in  strange  sur- 
roundings might  have  no  movements  of  the  stomach  for  two  or 
three  hours.  And  whenever  the  animals  showed  any  indications 
of  being  uncomfortable  or  distressed,  the  movements  were  in- 
hibited and  the  discharge  from  the  stomach  checked. 

Since  the  extrinsic  innervation  of  a  large  part  of  the  intestinal 
tract  is  the  same  as  that  of  the  stomach,  it  is  interesting  to  note 
the  effect  of  emotional  states  on  the  movements  of  the  intestines. 
Esselmont,13  in  a  study  of  the  dog's  intestine,  noted  constantly 
after  signs  of  emotion  a  marked  increase  of  activity  lasting  for 
only  a  few  moments.  Fubini 14  also  observed  that  fear  occa- 
sioned more  rapid  peristalsis.  The  increase  of  activity  in  the 
large  intestine  during  excitement  may  cause  uncontrollable 
voiding  of  the  gut.15  There  is  no  doubt  that  many  emotional 
states  are  a  strong  stimulus  to  peristalsis,  but  it  is  equally  true 
that  other  emotional  states  inhibit  peristalsis.  In  the  cat  the 
same  conditions  which  stop  the  movements  of  the  stomach  stop 
also  the  movements  of  the  intestines.  A  female  cat,  that  ordi- 
narily lies  quietly  on  the  holder,  and  makes  no  demonstration, 
will  occasionally,  with  only  a  little  premonitory  restlessness, 
suddenly  fly  into  a  rage,  lashing  her  tail  from  side  to  side, 
pulling  and  jerking  with  every  limb,  and  biting  at  everything 
near  her  head.  During  such  excitement,  and  for  some  momenta 
after  the  animal  becomes  pacified  again,  the  movements  both  of 
the  large  and  small  intestine  entirely  cease.  Such  violence  of 
excitement  is  not  necessary  to  cause  the  movements  to  stop. 
A  cat  wMch  was  restless  and  continually  whining  while  confined 


DEPRESSIVE    NERVOUS   INFLUENCES  219 

to  the  holder  showed  no  signs  of  intestinal  movements  during 
any  period  of  observation  (one  period  lasted  more  than  an  hour), 
although  the  changes  in  the  distribution  of  the  food  observable 
from  one  period  to  the  next  proved  that  movements  were  going 
on  during  the  quiet  intermissions.  In  another  cat,  uneasy  and 
fretful  for  fifty  minutes,  no  activity  was  seen ;  then  she  became 
quiet  for  several  minutes,  and  peristalsis  of  the  small  intestine 
appeared. 

When  the  segmentation  process  in  the  small  intestine  is 
stopped  by  excitement,  the  segments  unite  and  return  to  the 
form  of  a  solid  strand.  In  the  large  intestine  antiperistalsis  of 
the  proximal  portion  is  abolished  by  excitement,  possibly  because 
the  pulsating  tonus  ring  is  inhibited. 

Since  the  effects  of  impulses  coming  to  the  alimentary  canal 
along  extrinsic  nerves  have  been  studied  mainly  by  artificial 
stimulation,  it  was  of  interest  to  observe  the  results  of  physio- 
logical stimulation  during  emotion  after  different  nervous  con- 
nections had  been  destroyed.16    Under  these  circumstances,  such 
nerves  as  were  left  received  impulses  normally  and  delivered  them 
normally  to  the  peripheral  organ.     The  conditions,  therefore, 
were  highly  favourable  for  determining  the  course  of  inhibitory 
paths.    When  the  vagus  nerves  were  severed,  and  the  splanchnic 
nerves  alone  remained,  respiratory  distress  caused  the  usual  total 
cessation  of  the  movements  of  the  stomach  and  small  intestine. 
Impulses  along  the  splanchnic  nerves,  therefore,  physiologically 
inhibit  not  only  the  intestines,  but  the  stomach  as  well.    When 
the  splanchnic  nerves  were  cut,  and  the  vagi  alone  remained, 
respiratory  distress  had  no  effect  on  the  movements  of  the  small 
intestine  ;  but  when  the  distress  was  prolonged  until  the  animal 
began  to  toss  about,   gastric   peristaltic  waves  became  very 
shallow  or  momentarily  stopped.     From  this  evidence  it  would 
appear  that  the  inhibitory  impulses  of  the   vagi,   which  are 
physiologically  active  after  deglutition,  are  capable  of  acting 
also  in  states  of  turbulence,  although  they  are  not  nearly  so 
efficient  in  stopping  gastric  peristalsis  as  are  the  impulses  delivered 
by  the  splanchnics.     When  the  splanchnic  and  vagus  nerves  are 
all  cut,  the  movements  of  the  alimentary  canal  cannot  be  stopped 
by  respiratory  distress.     The  stoppage  in  theforniejL^ases 
not,  therefore,  be  attributed  to  any  other  *j&jjfr       .         .  „ 
influence-as,  for  example,  to  asphyxia. >f^^^^|||J^^f/} 
In  Pawlow's  investigations  of  the  wo 


220          THE   MECHANICAL   FACTORS    OF  DIGESTION 

the  importance  of  pleasurable  psychic  states  for  the  first  secretion 
of  the  gastric  juice,  on  which  so  many  processes  in  the  stomach 
and  intestines  depend,  was  strongly  emphasized.  It  is  probable, 
also,  as  I  have  indicated,  that  the  initial  tonus  of  the  stomach  is 
likewise  dependent  on  the  satisfaction  of  appetite.  These  results 
are  produced  through  nervous  influences  passing  down  the  vagi. 
The  opposing  influences,  reaching  the  alimentary  canal  by  way 
of  the  sympathetic  system  during  emotional  excitement,  can 
totally  destroy  both  the  secretory  17  and  the  motor  activities 
which  have  been  started  by  the  bulbar  system.  The  importance 
of  avoiding  so  far  as  possible  the  states  of  worry  and  anxiety, 
and  of  not  permitting  grief  and  anger  and  other  violent  emotions 
to  prevail  unduly,  is  not  commonly  appreciated,  for  the  subtle 
alterations  wrought  by  these  emotional  disturbances  are  unknown 
to  consciousness,  and  have  become  clearly  demonstrated  solely 
through  physiological  studies.  Only  as  the  consequences  of 
mental  states  favourable  and  unfavourable  to  normal  digestion 
are  better  understood  can  the  good  results  be  sought  and  the 
bad  results  avoided,  or,  if  not  avoided,  regarded  and  treated 
with  intelligence. 


REFERENCES. 

1  Cannon  and  Murphy,  J.  Am.  Med.  Ass.,  1907,  xlix.,  p.  840. 

2  Cannon  and  Murphy,  Ann.  Surg.,  1906,  xliii.,  p.  528. 

3  v.  Braam  Houckgeest,  Arch.  f.  d.  ges.  Physiot,.;  1872,  vi.,  p.  266. 
:     4  Liideritz,  Arch.  f.  path.  Anat.,  1889,  cxvi.,  p.  53. 

5  Bayliss  and  Starling,  J.  Physid.,  1899,  xxiv.,  p.  127. 

6  Cannon  and  Murphy,  J.  Am.  Med.  Ass.,  1907,  xlix.,  p.  840. 

7  Meltzer  and  Auer,  Proc.  Soc.  Exper.  Bid.  and  M.,  New  York,  1907,  iv., 
p.  39. 

8  Cannon  and  Murphy,  J.  Am.  Med.  Ass.,  1907,  xlix.,  p.  842. 

9  Cannon,  Am.  J.  Physid.,  1898,  i.,  p.  380. 

10  Cannon,  Am.  J.  Physid.,  1902,  viii.,  p.  xxii. 

11  Auer,  Am.  J.  Physid.,  1907,  xviii.,  p.  356. 

12  Lommel,  Munchen.  med.  Wchnschr.,  1903,  i.,  p.  1634. 

13  Esselmont,  Rep.  Brit.  Ass.  Adv.  of  Sc.,  1899,  p.  899. 

14  Fubini,  Untersuch.  z.  Naturl.  d.  Mensch.  u.  d.  Thiere,  1892,  xiv.,  p.  528. 

15  See  Darwin,  Expression  of  Emotions  in  Man  and  Animals,  New  York,  1873, 
p.  77. 

16  Cannon,  Am.  J.  Physid.,  1905,  xiii.,  p.  xxii;   Am.  J.  Med.  Sc.,    1909, 
cxxxvii.,  p.  485. 

17  See  Bickel  and  Sasaki,  Deutsche  med.  Wchnschr.,  1905,  xxxi.,  p.  1829. 


PUBLICATIONS 

FROM  THE  LABORATORY  OF  PHYSIOLOGY  OF  HARVARD 

UNIVERSITY,  BEARING  ON  THE  MECHANICAL 

FACTORS  OF  DIGESTION 


"  The  Movements  of  the  Stomach  Studied  by  Means  of  the  Rontgen  Rays." 

By  W.  B.  Cannon.     American  Journal  of  Physiology,  1898,  i.,  pp.  xiii-xiv, 

359-382. 
"  The  Movements  of  the  Food  in  the  (Esophagus."     By  W.  B.  Cannon  and 

A.  Moser.     American  Journal  of  Physiology,  1898,  i.,  pp.  435-444. 
"  The  Movements  of  the  Intestines  Studied  by  Means  of  the  Rontgen  Rays." 

By  W.  B.  Cannon.     American  Journal  of  Physiology,  1902,  vi.,  pp.  251-277. 
"  Observations  on  the  Mechanics  of  Digestion."     By  W.  B.  Cannon.     Journal 

of  the  American  Medical  Association,  1903,  xl.,  pp.  749-753. 
"  Further  Observations  on  the  Movements  of  the  Stomach  and  Intestines." 

By  W.  B.  Cannon.     American  Journal  of  Physiology,  1903,  viii.,  pp.  xxi- 

xxii. 
"  Salivary  Digestion  in  the  Stomach."     By  W.  B.  Cannon  and  H.  F.  Day. 

American  Journal  of  Physiology,  1903,  ix.,  pp.  396-416. 
"  The  Emptying  of  the  Human  Stomach."     By  W.  B.  Cannon.     American 

Journal  of  Physiology,  1904,  x.,  p.  xix. 
"  The  Passage  of  Different  Foodstuffs  from  the  Stomach  and  through  the 

Small  Intestines."     By  W.  B.  Cannon.     American  Journal  of  Physiology, 

1904,  xii.,  pp.  387-418. 
"  Gastro-enterostomy  and  Pyloroplasty  :  an  Experimental  Study."     By  W.  B. 

Cannon  and  J.  B.  Blake.     Annals  of  Surgery,  1905,  xli.,  pp.  868-911. 
"  Auscultation  of  the  Rhythmic  Sounds  Produced  by  the  Stomach  and  Intes- 
tines."    By  W.  B.  Cannon.     American  Journal  of  Physiology,  1905,  xiv., 

pp.  339-353. 
"  Recent  Advances  in  the  Physiology  of  the  Digestive  Organs  bearing  on 

Medicine  and  Surgery."     By  W.  B.  Cannon.     The  American  Journal  of 

the  Medical  Sciences,  1906,  cxxxi.,  pp.  563-578. 
"  The  Movements  of  the  Stomach  and  Intestines  in  some  Surgical  Conditions." 

By  W.  B.  Cannon  and  F.  T.  Murphy.     Annals  of  Surgery,  1906,  xliii., 

pp.  512-536. 
"  The  Motor  Activities  of  the  Stomach  and  Small  Intestines  after  Splanchnic 

and  Vagus  Section."     By  W.  B.  Cannon.    American  Journal  of  Physiology, 

1906,  xvii.,  pp.  429-442. 

"  Gastric  Peristalsis  in  Rabbits  under  Normal  and  some  Experimental  Condi- 
tions."    By  John  Auer.     American  Journal  of  Physiology,  1907,  xviii., 

pp.  347-361. 

221 


222          THE  MECHANICAL   FACTORS    OF  DIGESTION 

"  (Esophageal   Peristalsis   after   Bilateral   Vagotomy."     By   W.    B.  Cannon. 

American  Journal  of  Physiology,  1907,  xix.,  pp.  436-444. 
"  Physiologic  Observations  on  Experimentally  Produced  Ileus."     By  W.  B. 

Cannon  and  F.  T.  Murphy.     Journal  of  the  American  Medical  Association, 

1907,  xlix.,  pp.  840-843. 
"  The  Acid  Control  of  the  Pylorus."     By  W.  B.  Cannon.     American  Journal 

of  Physiology,  1907,  xx.,  pp.  283-322. 
"  Some  Observations  on  the  Neuro muscular  Mechanism  of  the  Alimentary 

Canal."     By  W.  B.  Cannon.     American  Journal  of  Physiology,  1908,  xxi., 

p.  xx. 
"  The  Acid  Closure  of  the  Cardia."     By  W.  B.  Cannon.     American  Journal 

of  Physiology,  1908,  xxiii.,  pp.  105-114. 

*'  Further  Observations  on  the  Myenteric  Reflex."     By  W.  B.  Cannon.     Ameri- 
can Journal  of  Physiology,  1909,  xxiii.,  pp.  xxvi-xxvii. 
"  The  Influence  of  Emotional  States  on  the  Functions  of  the  Alimentary 

Canal."     By   W.    B.    Cannon.     The  American  Journal   of  the   Medical 

Sciences,  1909,  cxxxvii.,  pp.  480-487. 
'"Some  Conditions  Affecting  the  Discharge  of  Food  from  the  Stomach."     By 

C.  A.  Hedblom  and  W.  B.  Cannon.     The  American  Journal  of  Medical 

Sciences,  1909,  cxxxviii.,  pp.  504-521. 
"  The   Physiological   Aspects    of   Gastroenterostomy."     By  W.  B.   Cannon. 

Boston  Medical  and  Surgical  Journal,  1909,  clxi.,  pp.  720-722. 
"  The  Correlation  of  the  Digestive  Functions."     By  W.  B.  Cannon.     Boston 

Medical  and  Surgical  Journal,  1910,  clxii.,  pp.  97-101. 
"  The  Effect  of  Severing  the  Vagi  or  Splanchnics  or  Both  upon  Gastric  Motility 

in  Rabbits."     By  John  Auer.     American  Journal  of  Physiology,  1910, 

xxv.,  pp.  335-344. 
"  Some  Observations  on  the  Nature  of  Gastric  Peristalsis."     By  W.  B.  Cannon 

American  Journal  of  Physiology,  1911,  xxvii.,  pp.  xii-xiii. 
"  The  Receptive  Relaxation  of  the  Stomach."      By  W.  B.  Cannon  and  C.  W. 

Lieb.     American  Journal  of  Physiology,  1911,  xxvii.,  p.  xiii. 


INDEX 


ABDOMEN  :  adaptation  of  capacity  of, 
to  increased  gastric  contents,  60;  hy- 
draulic relations  of  contents  of,  48 

Acid,  hydrochloric :  effect  of,  in 
stomach  in  closing  cardia,  39-42  ; 
in  opening  pylorus,  102-106 ;  in 
duodenum  in  closing  pylorus,  107- 
110  ;  gastric  discharge  of,  119 

Albumin  from  white  of  egg,  gastric 
discharge  of,  118-119 

Alimentary  canal,  activity  of,  when 
isolated  from  central  nervous  sys- 
tem, 210 

Alkaline  contents  of  stomach,  effect 
of,  on  peristalsis,  56 

Amylolysis  in  stomach,  71-74 

Anaesthesia,  effect  of  :  on  cesophageal 
peristalsis,  23  ;  on  gastric  discharge, 
211 

Anastomosis,  intestinal,  results  of 
end-to-end  and  lateral,  137-140 

Animal-holder,  6 

Antiperistalsis  :  of  stomach,  57,  192  ; 
of  small  intestine,  141-143  ;  of  large 
intestine,  149-156,  185-190;  rela- 
tion of,  to  tonus  ring,  186 

Anxiety,  effect  of,  on  peristalsis,  218 

Apomorphine,  use  of,  for  intestinal 
paralysis,  57 

Asthenia,  general,  effect  of,  on  move- 
ments of  gastro-intestinal  canal,  210 

Auerbach's  plexus.  See  Myenteric 
plexus 

Auscultation:  of  stomach,  166-170, 
177;  of  small  intestine,  170-173; 
of  large  intestine,  173-176 

Beer,  gastric  discharge  of,  119 

Bile,    effect    of    elimination    of,    on 

gastric  discharge,  108 
Bismuth  salts   in  X-ray  observation 

on  alimentary  canal,  5 

Caecum :  functions  of,  148  ;  effect  of 
irritation  of,  on  gastric  discharge, 
127 


Carbohydrate :  gastric  discharge  of, 
90 ;  when  mixed  with  protein,  93  ; 
when  mixed  with  fat,  94 ;  effect  of 
dilution  of,  on  gastric  discharge, 
121 

Cardia :  rhythmic  contraction  of,  32, 
35;  tonic  closure  of,  32-34;  after 
vagotoiny,  29  ;  relaxation  of,  33  ; 
conditions  affecting,  24-35 ;  vagus 
inhibition  of,  34 ;  action  of,  in 
eructation,  35 ;  periodic  relaxation 
of,  36 ;  closure  of,  by  acid  gastric 
contents,  39-42 

Cardiac  sac  of  stomach,  50  ;  salivary 
digestion  in,  72 

Cardiospasm,  35 

Cellulose,  effect  on  passage  of  food, 
146 

Chyme,  circulation  of,  after  gastro- 
enterostomy,  79 

Cold,  effect  of,  on  gastric  discharge, 
124-126,  212 

Colon.     See  Intestine,  large 

Consistency  of  food,  effect  of:  on 
deglutition,  16-18;  on  gastric  dis- 
charge, 120-123;  after  gastro- 
enterostomy,  77-78 

Cramps,  intestinal,  174 

"  Crossed  innervation  "  of  colon,  206 

Defalcation,  158-162 ;  innervation  of, 
206-207 

Deglutition :  mass  of  bolus  in,  9 ; 
movements  of,  11  ;  buccal  pressure 
in,  12 ;  discharge  theory  of,  13 ; 
sounds  of,  14  ;  in  different  animals, 
15-18  ;  rates  of,  with  different  con- 
sistencies of  food,  16-18  ;  effect  of, 
on  cardia,  33 ;  on  gastric  tonus, 
201 

Deglutition  reflex :  sensitive  spots  for, 
21  ;  afferent  nerves  of,  21  ;  resist- 
ance of,  to  fatigue,  21;  efferent 
nerves  of,  22  ;  centre  for,  22  ;  in- 
hibition of,  25;  as  affected  by 
stimulation  of  glosso-pharyngeus 


223 


224 


THE   MECHANICAL    FACTOKS    OF   DIGESTION 


nerve,  25  ;  in  relation  to  relaxation 
of  stomach,  201 

"  Digestibility  "  tables,  objections  to, 
87 

Digestion :  functions  of  mechanical 
factors  of,  1  ;  correlation  of  gastric 
and  duodenal,  112-120 

Distress,  effect  of,  on  peristalsis,  217 

Duodenum,  effects  on  gastric  dis- 
charge: of  acid  in,  107  ;  of  absence 
of  bile  and  pancreatic  juice  from, 
107-108  ;  of  destroying  continuity 
of,  with  stomach,  108-109 

Egg-albumin,  rate  of  gastric  dis- 
charge of,  118 

Emotions :  inhibition  of  gastrointes- 
tinal movements  by,  217-220 ; 
nervous  pathways  for  the  inhibi- 
tion, 219 

Enemata,  passage  of,  into  small  in- 
testine, 155-156 

Eructation  of  gas,  35 

Etherization,  effect  of,  on  gastric 
discharge,  211 

Excitement,  effect  of,  on  peristalsis, 
218 

Exposure  of  gastro -intestinal  tract, 
effect  of,  on  gastric  discharge,  211 

Fats :    gastric    discharge  of,    88-90 ; 

when    mixed    with    protein,     94 ; 

when    mixed    with    carbohydrate, 

94 ;   explanation  of  slow  passage, 

115-117 

Fear,  effect  of,  on  peristalsis,  218 
Food,    effect    on    gastric    discharge : 

of  consistency  of,  119-122;  of  hot, 

125 ;    of    cold,     125 ;     mechanical 

treatment  of,  in  small  intestine,  144; 

rate  of  passage  of,  through  small 

intestine,  145-146 
Foodstuffs,  mixed,  gastric  discharge 

of,  93-95,  114 

Gas  in  stomach :  effect  of,  on  gastric 
discharge,  123,  124  ;  in  large  intes- 
tine, 176 

Gastric  tube,  50 

Gastro  -  enterostomy :  gastric  peri- 
stalsis after,  75 ;  passage  of  food 
through  pylorus  after,  77-79  ;  cir- 
culation of  chyme  after,  79  ;  effect 
of  gastric  distension  on  stoma  in, 
79-80;  kinks  after,  80;  effect  of, 
on  pancreatic  digestion,  81 

Glosso-pharyngeus  nerves,  inhibitory 
to  deglutition,  25 

Haustra,  157,  158 
Hunger,  204 


Hydrochloric  acid :  effect  of,  on  cardia, 
when  in  stomach,  39-42  ;  on  pylorus, 
when  in  stomach,  102-106  ;  on  py- 
lorus, when  in  duodenum,  107-110  ; 
gastric  discharge  of,  119 

Hyperacidity,  effect  of,  on  gastric 
discharge,  119 

Ileo -colic  sphincter,  innervation  of, 
207 

Incisura  angularis  of  stomach,  46 

Incisura  cardiaca,  193 

Inhibition :  of  gastric  tomis,  201  ; 
reflex,  of  gastro -intestinal  move- 
ments, 261 

Innervation,  extrinsic  :  of  oesophagus, 
22-23;  of  stomach,  197-204;  of 
small  intestine,  204-205  ;  of  large 
intestine,  205-207 ;  of  sphincters, 
207-208  ;  "  contrary  "  and  "  recip- 
rocal," 179  ;  "  crossed,"  206 

Innervation,  intrinsic  :  of  oesophagus, 
26  ;  of  small  intestine,  178-185  ;  of 
large  intestine,  185-190 ;  of  sto- 
mach, 193 

Internal  anal  sphincter,  innervation 
of,  207 

Intestinal  pain,  203 

Intestine,  law  of,  179 

Intestine,  small :  effect  of  injury  of, 
on  pylorus,  126  ;  effect  of  irritation 
*of  caecum  on  passage  of  food 
through,  127 ;  length  of,  130  ; 
rhythmic  segmentation  in,  131- 
135,  182;  peristalsis  in,  135-137, 
183 ;  effects  of  end-to-end  and 
lateral  suture  of,  137-140;  activi- 
ties of,  when  obstructed,  140-141  ; 
antiperistalsis  in,  141-143 ;  effect 
of  severing  segments  of,  142 ; 
"peristaltic  rush"  in,  143;  mechani- 
cal treatment  of  contents  by,  144  ; 
passage  of  food  through,  145-146  ; 
regurgitation  into,  from  large  in- 
testine, 155-156  ;  rhythmic  sounds 
produced  by,  170-173 ;  intrinsic 
innervation  of,  178-185;  local 
reflex  in,  180 ;  rhythmic  contrac- 
tions of,  181  ;  neuromuscular  re- 
fractory period  of,  182  ;  effect  on, 
of  vagus  stimulation,  204 ;  of 
splanchnic  stimulation,  204 ;  of 
vagotomy,  205 ;  of  splanchnic 
section,  205 

Intestine,  large :  consistency  of  con- 
tents of,  149  ;  size  of,  in  different 
animals,  152 ;  antiperistalsis  in, 
149-156,  185-190;  tonic  constric- 
tions in,  149,  157  ;  passage  of  con- 
tents through,  157-158 ;  haustra 
of,  157,  158 ;  peristalsis  in,  158, 


INDEX 


225 


162,  185  ;  delayed  discharge  from, 
162  ;  sounds  produced  by,  173-1  7»>  ; 
local  reflex  in,  185  ;  effect  on,  of 
stimulation  of  sacral  nerves,  206  ; 
of  sympathetic  nerves,  206 ;  of 
cutting  sacral  nerves,  206  ;  of  cut- 
ting sympathetic  nerves,  206 

Kinks,  intestinal,  after  gastro-enter- 
ostomy,  80 

Laryngeus  nerves,  recurrent,  distribu- 
tion of,  to  oesophagus,  22 
Law  of  intestine,  179 

Manipulation  of  gastro-intestinaltract, 
effect  of,  on  passage  of  food,  213- 
214 

Mastication  :  duration  of,  under  vari- 
ous conditions,  8 ;  effects  of,  on 
food,  8  ;  on  salivary  flow,  9 ;  on 
subsequent  digestion,  10 ;  dental 
pressures  in,  9 

Methods  of  investigating  movements 
of  the  alimentary  canal,  4-7,  84-87 

Milk,  gastric  discharge  of,  115 

Mouth-pressure  in  deglutition,  12 

Muscle :  smooth,  characteristic  ac- 
tivities of,  when  intrinsically  inner- 
vated, 2,  181  ;  nature  of  tonus 
changes  in,  60  ;  action  when  de- 
prived of  my  enteric  plexus,  181 

Myenteric  plexus :  of  small  intestine, 
178-185 ;  of  large  intestine,  185- 
190  ;  of  stomach,  193 

Myenteric  reflex,  195 

Nicotine,  effect  of :  on  peristalsis  of 
small  intestine,  180 ;  on  anti- 
peristalsis  of  large  intestine,  186  ; 
on  gastric  peristalsis,  190 

Obstruction,  intestinal,  effects  of,  011 
intestinal  movements,  140-141 

(Esophagus :  functional  divisions  of, 
14,  18,  20 ;  innervation  of,  22 ; 
effects  of  anaesthesia  on,  23 ; 
primary  peristalsis  of,  24  ;  second- 
ary peristalsis  of,  24,  36  ;  paralysis 
of,  with  later  recovery,  after  vag- 
otomy,  25-29  ;  tertiary  paralysis  of, 
30  ;  regurgitation  into,  36,  43 

Pain,  intestinal :  174,203;  gastric,  202 
Pancreatic    digestion,    after    gastro- 

enterostomy,  81 

Paralysis :  oesophageal,  after  vag- 
otomy,  with  later  recovery,  25-29  ; 
post-operative,  211-215;  gastro- 
intestinal, from  manipulation,  after 
splanchnic  nerves  cut,  216 


"  Pendulum    movement  "    in    small 


Peristalsis,  3;  inhibited  by  i-moti'i-i  I, 
217-220  ;  <K8o)ilin<j,nl,  V.  ,/ 
20  ;  primary,  of  central  origin,  -J3, 
24  ;  secondary,  of  peripheral  origin, 
23,  24,  36;  effects  of  anaesthesia 
on,  23  ;  after  vagotomy,  26  et  seq.  ; 
tertiary,  under  local  control,  30  ; 
gastric,  51  et  seq.,  190-194  ;  rate  of, 
54-55  ;  with  different  gastric  con- 
tents, 55  ;  dependence  of,  on  tonus 
of  musculature,  56  ;  churning  func- 
tion of,  67  ;  after  gastro-enteros- 
tomy,  75  ;  passage  of  waves  of, 
192,  193  ;  in  small  intestine,  135  et 
seq.,  178  et  seq.,  183  ;  combined 
with  segmentation,  137  ;  rushing, 
136,  143  ;  regulation  of,  184  ;  in 
large  intestine,  158,  162  ;  passage 
of  waves  of,  187,  188  ;  regulation  of, 
190 

"  Peristaltic  rush,"  136,  143 

Physostigmine,  effect  of.  on  paralyzed 
intestine,  217 

Post-operative  paralysis,  211 

Pressure  :  intragastrtc,  in  eructation, 
35,  38  ;  normal  degree  of,  60-61  ; 
effect  of,  in  pyloric  vestibule,  after 
gastro-enterostomy,  77  ;  effect  of, 
on  gastric  peristalsis,  190,  191, 
192-193  ;  intra-abdominal,  unifor- 
mity of,  with  varying  abdominal 
contents,  60  ;  effect  of  voluntary 
increase  of,  on  position  of  viscera, 
161 

Proteins  :  rate  of  gastric  discharge  of, 
91-92  ;  when  mixed  with  carbo- 
hydrates, 93  ;  when  mixed  with 
fats,  94  ;  explanation  of  slow  pas- 
sage, 113,  114  ;  effect  of  dilution  of, 
on  gastric  discharge,  121,  122 

Psychic  tonus,  200 

Pyloric  canal  of  stomach,  46 

Pyloric  portion  of  stomach,  49 

Pyloric  vestibule  of  stomach,  46 

Pyloroplasty,  82 

Pylorus  :  selective  action  of,  69  ;  dis- 
charge through,  after  gastro-enter- 
ostomy, 77-79  ;  relaxation  of,  occa- 
sional, 96  ;  mechanical  agencies 
affecting,  97  ;  chemical  agencies 
affecting,  98  ;  theory  of  acid  control 
of,  100-101  ;  opened  by  acid  on 
stomach  side,  102-106  ;  closed  by 
acid  in  duodenum,  107-110;  corre- 
lating functions  of,  112-120;  tonus 
of,  115;  conditions  affecting,  120- 
128  ;  closed  by  intestinal  injury, 
126  ;  relaxation  in  absence  of  acid, 
127,  128  ;  innervation  of,  207 


226 


THE   MECHANICAL   FACTORS    OF   DIGESTION 


Rage,  effect  of,  on  peristalsis,  217,  218 

Rectum,  accommodation  to  contents, 
162 

Refractory  period  of  gastro-intes- 
tinal  neuromusculature,  182 

Regurgitation :  from  stomach  to  oeso- 
phagus, 36,  43  ;  conditions  for  it, 
37,  38  ;  from  large  to  small  intes- 
tine, 155-156 

Rhythmic  segmentation,  131-135, 
182  ;  sounds  produced  by,  170-173 

"  Rollbewegung  "  of  small  intestine, 
143 

Sacral  nerves:  supply  of,  to  colon, 
205 ;  effect  of  severance  of,  on 
colon,  206  ;  effect  of,  on  internal 
anal  sphincter,  207 
Saliva,  flow  of,  stimulated  by  mastica- 
tion, 9 

Salivary  digestion  in  stomach,  71-74 
Segmentation :  rhythmic,  in  small 
intestine,  131-135,  182;  combined 
with  peristalsis,  137  ;  in  proximal 
colon,  151  ;  haustral,  in  colon,  157, 
158 ;  sounds  produced  by,  170- 
173 ;  inhibition  of,  by  emotions, 
219 

Solids:  passage  of,  through  pylorus, 
69 ;  effect  of,  in  gastric  contents, 
on  gastric  discharge,  122 
Sounds  produced:  during  digestion, 
165  ;  by  stomach,  167-168  ;  by  small 
intestine,  170-173 ;  by  large  in- 
testine, 173-176 

Sphincter :  pyloric,  96  et  seq.  ;  ileo- 
colic,  154 ;  innervation  of,  207-208 
Splanchnic  nerves :  effect  of,  on  gastric 
tonus,  201  ;  on  small  intestine,  204, 
205  ;  on  pylorus,  207  ;  on  ileo-colic 
sphincter,  207 ;  as  pathways  of 
emotional  inhibition,  219 
Starch,  digestion  of,  in  stomach,  71-74 
Stomach :  mechanical  functions  of,  45 ; 
form  of,  45-47  ;  musculature  of,  46, 
47  ;  position  of,  47  ;  "  drainage  " 
of,  48  ;  two  parts  of,  49  ;  as  reser- 
voir, 50 ;  transverse  band  in,  51, 
52;  peristalsis  of,  51-56,  190-194; 
rate  of  peristalsis  in,  54,  55 ;  with 
different  contents,  56  ;  movements 
of,  in  vomiting,  57  ;  antiperistalsis 
of,  57  ;  adaptation  of,  to  amount 
of  contents,  59  ;  change  in  muscle 
fibres  of,  as  organ  fills,  60 ;  pres 
sures  in,  60,  61  ;  difference  in  con 
tents  in  two  ends  of,  62  ;  theory  o 
circulating  contents  of,  62,  64 
stratification  of  contents,  63,  64 
movements  of  contents  of,  63-67 
immobility  of  contents  of  cardiac 


end  of,   64  ;  absence  of  acid  from 
these      contents,      65 ;       churning 
function  of  peristalsis  of,  67  ;  secre- 
tion   of     and    absorption    by,    fa- 
voured    by     churning     peristalsis, 
68 ;    salivary   digestion   in,    71-74 ; 
movements  of,  after  gastro -enter  - 
ostomy,  75  ;  discharge  from,  after 
gastro  -  enterostomy,     77-79  ;     dis- 
charge of  different  foodstuffs  from, 
84-95 ;  discharge  of  fats  from,  88-90, 
115-117  ;  carbohydrates,  90,  91,  92  ; 
proteins,  91-92,  113-114;  mixtures 
of  foodstuffs,   93-95 ;   factors   con- 
cerned    in     discharge     from,     99  ; 
discharge  from,   delayed   by  delay 
of   acid   reactions   of   contents   of, 
102  ;  discharge  from,  hastened  by 
hastening  acid  reaction,   103  ;  dis- 
charge from,  preceded  by  acidula- 
tion  of  chyme,  104  ;  acid  in,  opens 
pylorus    in    excised    organ,     105  ; 
discharge  of  milk  from,  115  ;  water, 
117  ;     egg-albumin,     118 ;     hydro- 
chloric acid,  119  ;  beer,  119  ;  effects 
of    hyperacidity    on    gastric    dis- 
charge   from,     119-120;     of    food 
consistency,    120-122 ;    of    gas    in 
stomach,  123-124 ;  of  hot  and  cold 
food,  125  ;  of  irritation  of  caecum, 
127  ;  sounds  produced  by,  167-168  ; 
innervation    of,    by    vagus  nerves, 
197  ;    by  splanchnic   nerves,  201  ; 
tonus    of,    from    vagus    impulses, 
199  ;    inhibition  of,  by  splanchnic, 
201  ;  relaxation  of,  after  swallow- 
ing, 201  ;  question  whether  source 
of  sensations    of    heat,    cold,    and 
pain,  202-203  ;  size  of  fasting,  204  ; 
discharge  from,  after  etherization, 
211  ;   after   exposure   to   air,   211- 
212 ;     after     cooling,     213 ;     after 
manipulation,  213-214  ;  after  mani- 
pulation with  splanchnics  cut,  216 
Sympathetic  nerves,   distribution   to 
colon,  205  ;  effect  of  severance  of, 
206 ;    effect   of,    on    internal    anal 
sphincter,  207 

Temperature,  effect  of,  on  gastric 
discharge,  125 

Tension :  importance  of,  for  oesopha- 
geal  peristalsis,  28  ;  as  a  condition 
favourable  to  contraction,  182,  187, 
188-189,  191,  192 

Tonus :  importance  of,  for  movements 
of  colon,  188 ;  of  stomach,  191, 
200-201  ;  of  small  intestine,  195  ; 
of  alimentary  tract,  210  ;  in  digest- 
ing stomach,  191,  194  ;  relation  of 
gastric,  to  vagus  impulses,  199 


INDEX 


227 


Tonus  ring :  in  large  intestine,  149, 
157  ;  pulsations  of,  186  ;  as  source 
of  antiperistalsis  in  large  intestine, 
186  ;  refractory  to  stimulation, 
188 ;  origin  of,  189  ;  as  source  of 
gastric  peristalsis,  193-194 

Transverse  band  of  stomach,  51,  52 

Vagotomy :  effects  of,  on  oesophagus, 
26  et  seq.  ;  effects  on  cardia,  29, 
34  ;  effect  on  stomach,  199 

Vagus  nerves :  distribution  of,  to 
oesophagus,  22  ;  to  stomach,  198  ; 
effects  of,  on  cardia,  33-34 ;  effect 


of  stimulation  of,  on  gastric  ton  us. 
198 ;  function  of,  in  relation  to 
stomach,  199,  201  ;  effect  on  small 
intestine  of  stimulation  of,  204  ;  of 
severance  of,  205 ;  effect  of,  on 
pylorus,  207  ;  as  pathway  for 
emotional  inhibition,  219 
Vomiting,  56,  57  ;  faecal,  142 

Water,  gastric  discharge  of,  117 

X-ray  methods  of  studying  move- 
ments of  the  alimentary  tract, 
5-7,  84-87 ;  consideration  of  objec- 
tions to,  86,  87 


THE   END 


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